Nautical Terminology and Definitions
As found in Chapman Piloting 62nd Edition by Elbert S. Maloney
Rewritten for the web by Matt Ursin.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
abaft- Behind, toward the stern
abeam - To one side of a vessel, at a right angel to the fore-and-aft line
abreast - Even with, by the side of, side by side
ABYC - American Boat and Yacht Council, Inc., The organization that sets voluntary safety and construction standards for small craft in the USA
admeasure - To measure a vessel for the purpose of documentation
adrift - floating free without propulsion; not moored, aground, nor fastened to the shore
admiralty law - Law of the sea; a term for maritime law derived from the British Admiralty department, which administers naval affairs
aft, after - Near or at the stern
after bow spring line - A mooring line running aft from a point at or near the bow to shore to control forward or backward motion of a vessel in it's berth
agonic line - An imaginary line on the Earth's surface, along which there is no magnetic variation
aground - With the keel or bottom fast on the sea bottom
aids to navigation - Markers on land or sea that are established to enable navigators to avoid dangers and fix their position; buoys, lights, beacons, radiobeacons, daybeacons with known charted positions
aloft - Above the deck, usually in the rigging
amidships - In the center, the center portion of a vessel
anchor - A heavy metal device, fastened to a chain or line, to hold a vessel in position, partially because of it's weight, but chiefly because of it's designed shape digs into the bottom
anchorage - A customary, suitable and (usually) designated harbor area in which vessels may anchor
anchor bend - A specific knot, generally used to fasten an anchor line to an anchor
anchor light - An all-round white light required by the Navigation Rules when a vessel is at anchor or moored; also called a riding light
anchor rode - A line, chain or steel cable used to hold a vessel fast to the anchor
anchor watch - Person or persons kept alert on deck while the vessel is at anchor or moored in order to cope with unexpected situations
anemometer - A instrument that measures wind velocity
aneroid barometer - A device to measure and indicate air pressure for meteorology, using a mechanical means, rather that a liquid such as mercury
anti-fouling - a type of paint, used at the bottoms of boats, that repels barnacles, marine grass and many other undesirable adhesions
apparent wind - The direction and force of the wind relative to a moving vessel, differing from true wind, The motion of a sailboat or powerboat under way make the effective wind, acting on sails or hull, vary from the actual wind. Apparent wind can be indicated by by a telltale or instruments
astern The direction toward the stern of a vessel, or beyond the stern
athwart - At right angels to the center line
autopilot - An automatic steering device. The heading of a boat is sensed by a compass and the craft is steered to maintain a present course by a combination of electronic and mechanical/hydraulic devices; on sailboats a similar system is used to steer a course based on the apparent wind
auxiliary - A sailboat that has an engine
aweigh - Off the bottom, said of an anchor
B
Backing (wind) - Wind changing it's direction, counter-clockwise in the northern hemisphere, clockwise in the southern hemisphere; opposite of veering
backsplice - A splice in which the strands are reversed and interwoven, to make a rope end
backstay - A stay supporting the mast, running from the masthead to the stern
ballast - Additional weight placed in the hull to improve stability; ballast may be either internal or external
bar - a sand, mud, or debris shoal, as across the mouth of a river or harbor
barograph - A weather instrument that continuously records atmospheric (barometric) pressure>
barometer - An instrument that measures and displays atmospheric pressure, showing it in millibars (or in inches or in millimeters of mercury) usually on a dial with an indicating needle
batten down - To close all openings, such as hatches, and fasten all lose gear, in heavy weather; wooden hatches used to be covered with battens and wedges
battens - Thin flexible strips of wood or plastic, used in batten pockets of sail to support (stiffen to keep flat) the roach; battens are also used in awnings
beam - One of the principal dimensions of a boat, the width; also, the direction at right angles to the centerline of a vessel, as "the lighthouse is broad on the beam"
beam reach - A point of sailing with the apparent wind blowing at right angles to the boat's fore-and-aft line
bearing - The direction of an object (vessel, buoy, etc.) from an observer; bearing can be visual, or by radio or radar
bear off - To turn away from the wind, to turn leeward, also "to bear away"
beating - Sailing against the wind, in alternate tacks
Beaufort wind scale - A scale indicating the force of the wind, invented by Admiral Beaufort in 1808; the original scale indicated the effect of a full-rigged frigate under sail; it has been extended to cover effects on shore as well as sea, plus criteria that can now be measured, such as speed of the wind; the scale usually shows wind forces 0 through 12, but it has been expanded to 17. Each increase of force (number) means a doubling of the pressure (not velocity) of the wind
becket - A loop or eye made in the end of a rope or wire; a rope handle
bedding compound - Caulking material used for matting two surfaces, rendering them watertight
bend - One of several types of knots, a combination of turns and tucks, used to fasten a line to a spar or another line; to fastenby meqns of a bend or knot
bend on - To prepare a sail for hoisting; to rig
berth - A position, as a place to sleep or which a vessel may be made fast; a margin of safety; as "wide birth"
bight - The middle part of a slack rope; a loop; an indention in a shoreline
bilge - The lowest point of a vessel's interior hull; also the part of the exterior between the bottom and the topsides, the "turn of the bilge"
binnacle - A compass box or case, or a stand usually illuminated at night
binocular - A telescopic instrument for the use of both eyes at once, having two tubes, each furnished with lenses. It usually prisms as well as lenses to keep the size down
bitt - A strong post of wood or iron, similar to a samsonpost, on deck, in the bow or stern, to which anchor, mooring and towing line may be fastened
bitter end - Inboard end of an anchor rode, the extreme end of any line
block - Complete assembly of sheaves or pulleys and shells (plates) on which ropes run; can be wooden, plastic or metal
block-and-tackle - Any of several arrangements of blocks (pulleys) and line to gain mechanical advantage
boarding ladder - A temporary set of steps lowered over a vessels side
boat - A small vessel, propelled by oars, sail or power; a vessel that can be carried on board a ship
boathook - A hook on a pole, used for retrieving or picking up objects and for fending off
bollard - A strong vertical fitting, usually iron, on deck or on a pier or wharf, to which mooring lines can be fastend
boom - A spar used to extent the foot of a sail
boom vang - A system of fitting to hold the boom down under some sailing conditions
boot-top - A painted stripe at the waterline
bosun - A boatswain, a petty officer in charge of hull, rigging and sail maintenance as well as deck operations; other phonetic spellings are bos'n, bo's'n, bo'sun
bosuns chair - A seat, sometime a rigid plank, sometimes made of canvas, used to hoist a person aloft to repair rigging; pockets for tools are often included
bosun's locker - A shipboard storage area for deck supplies, paint, rigging fittings and tools
bow - The forward part of a boat
bow & beam bearings - A set of bearing on an object ashore or an aid to navigation whose position is known, used to determine distance off
Bowditch - A standard work on navigation, containing useful tables and instructional text; it is named after Nathanial Bowditch, the nineteenth-century author of "Bowditch"
bowline - The "king of knots," used used to make a loop in a line; this knot is simple, strong, virtually slip-proof and is very easily untied
bowsprit - A fixed spar, projecting from the bow, to which forestays and/or the headstay are fasted; also useful for anchor handling
braided line - A modern configuration of rope (usually called a line aboard a boat or ship); it may be a single braid or double braid, one braid (core) inside another
breakers - Waves cresting as they reach shallow water, as at or on a beach
breakwater - A structure, usually stone or concrete, built to create a harbor or improve an existing one
breast line - Mooring or dock line, extending laterally from the vessel to the pier or float, as distinguished from a spring line, which controls fore and aft movement of the vessel
bridge - The control station of a vessel; the persons in charge of a vessel, or (by extension) of an organization, such as the U.S. Power Squadrons; a structure over water to carrypedestrian, vehicular or railroad traffic
brightwork - Polished brass, bronze or stainless steel aboard a vessel; also, varnished wood as trim
Bristol fashion - Shipshape, clean, neat, orderly and conforming to high standards of seamanship
broach to, broaching - The sudden, unplanned and uncontrolled turning of a vessel so that the hull is broadside to the seas or to the wind
broad on the beam - At a right angle to the vessel
broad reach - A point of sailing with the apparent wind broad on the beam
bulkhead - A transverse wall in the hull; the interior compartmentalization of a vessel is created by bulkheads; in some cases bulkheads are watertight, adding to the safety in case of damage to the hull
buntline hitch - A simple, useful hitch for attaching a halyard to a shackle; strong secure, easily undone
buoy - A floating aid to navigation showing channels or otherwise indicating location, rocks and other obstructions, and prohibited areas in the water; turning points in races; to buoy the anchor is to
temporarily fasten the anchor line to a float, so that the anchor need not be raised when a vessel is leaving it's anchorage
burdened vessel - The vessel which must "give way" to another vessel in a crossing or overtaking situation, following the Navigation Rules
burgee - A special flag flown on a vessel or on a flagstaff of a shore installation, indicating either the ownership of the vessel or the identity of a yacht club or similar organization
C
camber - Curvature of either sail or keel; the curve of the deck, usually being higher in the center so that the water can run off
can - A cylindrical buoy, generally green
Canadian Power & Sail Squadrons - A private membership organization that specializes in boating education and safe boating practices
canvas - Firm, closely woven cloth (originally hemp, linen or cotton) used for sails and awnings; a set of sails; today the word "sailcloth" is generally used for modern sail-making fabrics such as polyester (Dacron) and nylon
capsize - To turn over; to turn bottom side up
capstan - A vertical winch on deck; used for hauling, such as the anchor line
carbon fiber - Modern fiber used with epoxies in order to stiffen a component
cardinal points - The four principal compass points: North, South, East and West
carlins - Fore and aft members of the deck frame; they support the coamings of the cockpit, the cabin trunk sides and the hatch coamings
carric bend - A useful knot for fastening two lines together; a number of variations exist, but these are of little or no value
carry away - To break lose, said of gear that is stressed beyond the strength of it's fastenings
carvel - Smooth skin planking
cast off - To loose, unfasten; to undo all mooring lines in preparation of departure
catalyst - Chemical used to activate polyester resins and other polymers
catamaran - A twin-hulled vessel, sail or power
catboat - A simple rig for a sailboat, with one mast and one sail which may be either Marconi or with a gaff
catenary - In a rope or chain run between two points, the sag from a straight line due to the effect of gravity
cavitate, cavitation - Turbulence in the water caused by rotation of a propeller; causes wear on the propeller and a reduction in propeller efficiency
ceiling - The inside lining of the hull
celestial navigation - Position determination (and the total process of navigation based on it) by reference to sun, stars and moon. Usually a sextat measures the altitude of the observed heavenly body, a highly accurate source of time information is used to determine the time of the sight, and tables and/or a navigational electronic calculator are used to determine a position line; the place where two position lines cross is a fix
centerboard - A board or metal plate, moving vertically or pivoting up and down in a slot in the keel, which adds lateral resistance to the hull form of a sailboat; in effect the boat's sideways motion through the water is thus controlled by increasing the area of the keel
certificate - A government paper, such as a boat's license, or a seaman's or master's license allowing the operation of a commercial vessel
chafe - Abrasion, wear
chafing gear - Cloth, tape or other material fastened around a line or other rigging to prevent wear
chain - Interlocking steel or iron links, used for anchor rodes and, on larger vessels, certain rigging parts
chain locker - Stowage space for anchor chain
chainplates - Fittings on the sides of the hull or the outer edges of the deck of a sailboat, to which the port and starboard rigging, called shrouds, are fastened
chandlery - Items of nautical gear or the shop where these are sold
channel - The navigable portion of a waterway; the marked and designated area where there is a known depth of water; boats may not normally anchor in a channel
Charlie Noble - A stovepipe fitting in a cabin top or deck, through which the metal "chimney" of a boat's cooking or heating stove passes; usually equipped with a cooling rim of water and partial cap, to exclude rain and control smoke
charts - Seagoing maps; most charts are issued by government sources, and their data is based on surveys of the land and underwater areas, showing depths as well as buoys and other aids to navigation; they are updated periodically
chart table - Also called navigation table, where charts are handled for the purpose of navigating
chine - The intersection between the topsides and bottom
chock - A rigging fitting, essentially shaped like a U or an O, normally mounted on deck or in the toe rail, to control a rigging mooring line
chockablock - Full up, tight, drawn up as far as possible, as when two blocks in a tackle are closed up and no more movement of the line is possible
chop - Short, steep waves
clamp - The inner longitudinal timber or plank in the construction of a wooden vessel that acts as the bearer for beams or joints
classes - Organized groups of boats (essentially for racing), with either identical measurements and specifications, or variable measurements to fit a formula, designed to equalize boat performance to some degree and thus put a premium on skill and tactics
cleat - A rigging fitting to which mooring lines, sail control lines such as sheets and halyards, and miscellaneous lines are temporarily attached
cleat hitch - The distinctive crisscross or figure-eight hitch used to fasten (belay) a line to cleat
cleveis pin - A large pin that secures one fitting to another
clew - The lower, after corner of sail, to which the sheet is attached
close-hauled - Hard on the wind, a point in sailing in which the sheets are hauled tight, enabling the boat to sail "against the wind"
clove hitch - A double-loop hitch, generally used around a piling or bollard; easily adjusted, but it can work lose
club-footed - Foot of sail, such as a jib or foresail, supported by a small boom
coaming - A raised edge, as around part or all of a cockpit, that prevent the seawater from entering the boat
Coast Pilots - Reference books, issued by the U.S. National Ocean Service, listing navigational aids and other information useful in coastal piloting; the nine books (covering East, Gulf and West coasts, Hawaii and Alaska) including sailing directions, recommended courses, distances between ports, channels, harbors and anchorages
cockpit - A space for the crew, lower than the deck and often water tight or self draining
cockpit sole - The actual floor of a cockpit
code - In signaling, any of several systems used to transmit messages visually, by sound or electronically; alphabet code flags and dot-dash (Morse) systems are most often used; in addition to spelling out words, code flags are used in combinations to transmit brief phrases or to describe marine situations such as emergency conditions
cold front - A term used in weather reporting/forecasting to describe the forward edge of a mass or cold air meeting warmer air; as the warmer air is forced upward, heavy clouds are formed, often bringing rain and strong winds
cold molding - Process of bending multiple thin layers of wood in sequence with glue to achieve a total desired thickness as opposed to forming by steam bending or sawing
colors - The national ensign; the act of ceremony of raising the colors, including other flags
COLREGS - U.S. Coast Guard term for International Regulations for Preventing Collisions at Sea, also known as the Navigational Rules of the Road
come about - To tack, to change direction relative to the wind
companionway - A hatch or entrance, from deck to cabin
compass - Navigation instrument, either magnetic needles or bars attached, which floats or pivots on a bowl; older compasses used a system of graduated points while most modern ones use the 0-360 degree system; a plotting tool used to draw circles or circular objects
composite construction - Made with more than one component and of different nature, e.g. plywood and fiberglass
cordage - A term that includes all rope and small line, whether made of natural or synthetic fibers
cored construction - The use of a core material sandwiched between an outer layer, e.g. deck made of fiberglass inner and outer layers and balsa core
Corinthian - An amateur yachtsman
cotter pin - A small pin used to secure a clevis pin and to keep turnbuckles from unwinding; a small pin used to keep any nut from backing off
counter - The portion of the hull, at the stern, above the water line and extending aft
course - The direction in which a vessel is to be steered; in racing, the preset course or series of courses, often triangular, to be followed
cowls (scoops) - Direct the flow of air and vapors in or out of ducts
cradle - A frame used to support a vessel on land
crest - Top of a wave
cringle - A rope loop or circular eye, made on a metal or plastic thimble, used for fastening on the corner of a sail, awning or other canvas idem
crossing situation - When two vessels meet, not head on or nearly head on, but with each having the other forward of a direction 22.5 degrees aft the beam; the vessel having the other on it's starboard side is the give-way vessel and must keep clear
cunningham - A line controlling tension along a sail's luff, invented by Briggs Cunningham
current - Horizontal movement of water, as from the normal flow of a river or when caused by the rise and fall of tides
D
DRS - Sail known as a drifter/reacher/spinnaker
Dacron - Trademark name for a type of polyester
daggerboard - A centerboard that is retracted vertically rather than hinged
danger angle - A piloting angle, in which on both chart and the water a measured angle between the two directions to two points - such as buoys, landmarks or rocks - indicates the mariner an unsafe limit for his/her vessel
davit - a swung out device, a crane, used to hoist; a pair of davits, at the stern or at the side of a vessel, handles a dingy or other small boat; a single davit at the bow is often used to handle a heavy anchor
dayboard - A sign with a specific geometric shape atop a pile or dolphin as part of an aid to navigation; the combination of the dayboard and pile or dolphin if unlighted is a "daybeacon," if lighted it is termed a "light"
daysailer - A boat without a cabin that is used for short sails or racing
dayshape - A special geometrical marker, such as a black ball, cone or cylinder hung aloft to indicate a vessels type, occupation or state; one ball means "at anchor," three means "aground"
dead ahead, dead astern - Directions exactly ahead or behind a vessel
deadlight - A fixed skylight, comparatively small, in a deck or cabin top, admitting light to the space below; a non-opening port
dead reckoning - The navigation means used to determine position, calculated from the course steered and the speed through the water, with out obtaining a fix; a dead reckoning position is indicated on a chart by marking a half half circle with a dot on the track line; the time is placed at an angle to the horizontal and to the track line
deadrise - Height between the bottom of a vessel and its widest beam, also expressed as an angle
departure, point of - The last fix obtained by an outward bound vessel; it is marked on the chart as the beginning of the track until the next fix or estimated position
depth sounder - An electronic depth finding instrument, measuring the time a sound wave takes to go from the vessel to the bottom and return, then displaying the result in feet, fathoms and meters
deviation - The amount by which a ship's magnetic compass needle points to one side or the other of magnetic north; iron, steel magnetsand DC currents in wires cause the compass to vary by different amounts on different headings
dinghy - A small boat used as a tender; the term is also used for a small racing sailboat
displacement - The weight of the water displaced by a floating hull; the volume of the water will vary depending on whether it is fresh water or seawater
displacement hull - A boat supported by its own buoyancy while in motion
distress signals - Standardized or improvised signals, which may be visual, audible or electronic, that are used on board a boat to indicate distress and seek assistance; various signals are listed in Navigational Rules
ditty bag - A small bag for tools and personal items
dock - An enclosed or nearly enclosed water area; all the port installations; a place where vessels can make fast, as at pier, wharf or floating dock
documentation - A special federal license or registration for a vessel
dolphin - A small group of piles, in the water, tied together in a single structure, generally used for mooring or as a part of an aid to navigation
Dorade vent - Designed deck box ventilation to keep water out with a baffle while letting air in below decks
double braid - Rope made with braided core and a braided cover, usually of synthetic fibers
double-ender - A design of a boat with a sharp stern, resembling the bow in configuration
douse - To drop or lower a sail quickly; to put out a lamp or fire
downhaul - A rigging line used to haul down, or to hold down, a spar or sail
downwind - A direction to leeward, with the wind
draft - The vertical distance from the water line to the lowest point of the hull or attachments such as propellers and rudders, thus the minimum depth of water in which a vessel will float; a vessel is said to "draw" a certain amount of water; the curvature built into a sail
drift - A current's velocity
drogue - An open-ended cone, usually canvas, serving to slow a boat in heavy weather
drydock - An enclosed dock from which the water can be pumped out, so a ship can be repaired and cleaned
dry rot - Decay of wood timbers, as in a boat, actually occurring in moist conditions
drysail - Drying out the boat after each sail outing
dry storage - Storing on land, out of the water
ducts - Channel movement of air for the actual displacement of fume from the space being ventilated
E
ease - To let out a line under full control, gradually as with a sheet or a docking line
ebb - A tidal current flowing toward the sea
electronic navigation - Piloting by manual or automatic electronic devices: echo sounders, electronic compass, radio direction finder, radar and various position-finding systems such as Loran-C, Omega, Decca, VHF Omnirange (VOR) and satellite systems
ensign - The national flag, or that of an organization such as the Coast Guard Auxiliary or the U.S. Power Squadrons
entry - Forward-designed section of hull in the water; qualifies the type of the hull in terms of efficiency and behavior in relation to wave action (for example, a sharper entry means faster hull speed for a racing hull)
EPIRB - Emergency Position Indicating Radio Beacon, a small continuously operating transmitter, using a standard distress frequency to alert authorities to the existence of a distress situation and to lead rescuers to the scene
estimated position (EP) - A navigational point (less precise than a fix) based on course run, speed and estimates of such factors as drift caused by winds or currents
eye splice - A fixed loop in the end of a line, made by intertwining strands of rope or by tucking an outer core of double-braid rope back into itself
F
fairlead - A rigging fitting designed to change the direction of line, control the line and minimize friction
fastening - Any of several methods of holding planks in a wooden boat to the frames: screws, nails, rivets; a screw or bolt used to fasten rigging and plumbing fixtures
fathom - A nautical linear measurement, 6 feet, used primarily to measure depth and anchor rodes
Fathometer - The trademark name for one brand (Raytheon) of electronic instrument for measuring depth in water
FCC Rules - Regulation of the Federal Communications Commission in the U.S. that govern radio equipment and radio operations
fender - The cushioning device hung between the boat and a float, pier or other craft
fetch (1) - To sail a course that will clear a buoy or shoul, also "lay"; (2) the distance across water over which the wind is or has been blowing
fiberglass - Fiber-reinforced plastic; glass in fibrous form, usually reinforced with synthetic resin such as polyester; may be woven or mat form
fid - A tapered printed tool used to separate strands of rope, as in splicing
figure-eight - A knot, usually in the end of a line from passing through a block or fairlead
fin keel - Keel shaped like the fin of a fish, shorter and deeper than a full-length keel
finger pier - A narrow pier projecting from the shore or at right angles from a larger pier
fix - The position of a vessel, determined by bearings, either visual or electronic, or by any other means believed to be acceptably accurate
flame arrester - A safety device, such as a metal mesh protector, to prevent an exhaust backfire from causing an explosion
flare - A pyrotechnic signal that can indicate distress; the outward curvature of the topsides
flashing - A light that is on less than it is off in a regular sequence of signal flashes, occurring less than 30 times in each minute
flemish - To coil a line spirally, laid flat on the deck, either for appearance or to make a mat
flinders bar - A soft iron bar, in or on the binnacle, to compensate for compass error from vertical magnetism in a vessel with a steel hull
flood - The rising, incoming tide
floor - Structural members in the bottom of a boat, running athwartships from bilge to bilge
flotsam - Wreckage debris floating on the water
fluke - The flat palm-shaped or shovel-shaped part of an anchor (on the end of each arm) that digs into the bottom to prevent dragging
flush deck - Deck without any superstructure
flying bridge - A high steering position, usually above the normal wheelhouse or a power cruiser; also called flybridge
following sea - Waves from astern
foot - The bottom edge of a sail; also, to steer slightly lower than close-hauled in order to increase boat speed
fore - Located at the front, as of a vessel
fore-and-aft - From stem to stern, from front to back, oriented parallel to the keel
forecabin - Forward cabin of a boat as opposed to aft cabin
forecast - Formalized weather prediction
forecastle - The forward portion, below decks, of a vessel; the place where the crew is quartered. Pronounced and sometimes spelled fo'c'sle
foredeck - The forward part of the main deck of a vessel
forepeak - The extreme forward compartment of a vessel, usually used for stowage
forestay - A stay, from high on the mast to the foredeck; the headstay runs from the top of the mast to the bow and is the outermost stay
forestaysail - A sail attached to the forestay, similar to a jib, which is on the headstay
foretriangle - The area bounded by the mast, foredeck and headstay
forward - On board a vessel, the direction to the front, toward the bow
forward quarter spring line - A mooring line running forward from the quarter to control the forward and backward motion of a vessel in its berth
founder - To sink
fractional rig - A rig in which the jib of a sloop does not reach to the top of the mast, a three-quarter rig is an example of this rig
frames - Ribs; transverse structural members of a vessel
freeboard - The vertical distance between the waterline and the top of the deck
fronts - Boundaries between air masses that have different temperatures
fully battened - Sail with batten running full length of the sail horizontally
furling - Folding, rolling or gathering a sail on its boom when it is not in use
G
gaff - A spar holding the upper side (head) of a four-sided sail; a device used to boat a large fish
galley - The kitchen on a boat or ship
garboard strake - The strake (plank) next to the keel
gel coat - Standard finish of a fiberglass boat
genoa - An overlapping jib
geographic position - Charted position
gimbals - Pivoted rings holding a compass or other device so that it can tip in any direction or remain level when the support tips
give-way vessel - The vessel that does not have the right of way in a crossing or overtaking situation; the vessel that is burdened
Global Positioning System (GPS) - A worldwide radionavigation system of high accuracy using orbiting satellites
grab rail - A convenient grip, on a cabin top or along a companion ladder
granny knot - A faulty knot, often tied in error; it is not sure to hold, nor is it always easy to unfasten; neophytes confuse it with a square knot
great circle - A circle formed on a sphere, such as the earth, by the intersection of a plane passing through the center of the sphere; an arc of a great circle is the shortest distance between two points, hence a great circle route is the shortest route between the points
grommet - A ring or eyelet, as in a sail; a rope grommet is a circle made by unlaying the rope, then using one strand spirally, twisting onto itself, replacing the original strands
gross tonage - The tonal interior space of a ship, including non-cargo space, computed at 40 cubic feet equals one ton; net tonage is found by subtracting engine rooms. crew's quarters, stores and navigation space; displacement tonage is the weight of the vessel, which is the same as the weight of the water displaced
ground swells - Swells that become shorter and steeper as they near the shore, because of the shoaling water
ground tackle - Anchor, anchor rode (line or chain) and all the shackles and other gear used for attachment
gunwale - The upper edge of the side of a boat, usually a small projection above the deck; toe rail
guy - A rigging line for control, attached to the end of a moveable spar
gyres - Giant, circular oceanic current
H
hail - To call a ship or boat
half-hitch - The simplest knot, usually part of another knot, as two half hitches or a fisherman's bend
halyard - A line used to hoist a spar or sail aloft
hand bearing compass - A portable compass, used primarily for sighting or taking bearings
hand lead - A weight, attached to a line, lowered into the water to find out the depth
handsomely - Slowly and carefully, as to "ease a line handsomely," in a proper manner
handy-billy - Block and tackle (moveable)
hanging locker - A storage place for clothing
hank - Small snap hook securing the jib luff to the headstay
harbor - A safe anchorage, protected from most storms; may be natural or man-made, with breakwaters and jetties; a place for docking and loading
harbormaster - The person in charge of anchorages, dock spaces, refuse collection and similar matters
hard-chined - Hull shaped with flat panels joined at an angle
hard over - All the way in one direction, as a tiller or wheel can be "hard over" to make an abrupt turn
hatch - A deck opening providing access to the space below; normally a hatch cover, hinged or sliding, is fitted
hauling - Hauling out is removing a boat from the water; pulling on an anchor line, halyard, or a rope or line is simply called hauling
hauling part - The part of a fall or tackle to which power is applied
hawse hole - An opening in the hull, through which mooring lines are run
hawsepipes - fittings in the hawse holes through which dock or anchor lines may be run, and, in larger vessels, in which the upper part of the anchor may be stowed
hawser - A large diameter rope, generally 4½ inches or larger, used for towing and dock lines on larger vessels
head - The bow or forward part of a vessel; the upper end of the vertical part, such as rudder head; the upper corner of a triangular sail; the upper edge of a four-sided sail; the toilet aboard ship (fixture only or entire compartment)
heading - The direction in which a vessel is pointed at any given moment
headsail - Any of several sails set forward of the mast, or in the foretriangle
head seas - Waves coming from the direction in which a vessel is heading
headstay - A stay from the bow to a point high on the mast; the foremost stay
headway - Forward motion of a vessel through the water
heave - To pull strongly on a line; to throw a line
heaving line - A light line, coiled and thrown from vessel to vessel or between vessel and shore, to be used for pulling a larger line, such as a dock line
heavy weather - Stormy, windy weather, usually connoting rough or high seas and danger or discomfort
heel, heeling - To tip, to lean to one side; heeling may result from uneven distribution of weight or the force of the wind; a list is a continuous condition; a roll is a repeated inclination, from side to side
heeling error - The additional or changing deviation in a compass caused by heeling, when the relative position of heavy iron (keel, engine) is changed so that the magnetic forces varies
helm - The tiller, wheel, and other steering gear; a boat is said to have a weather helm if it tends to turn its bow to windward, lee helm if it tends to fall away from leeward
helmsman - The person (man or woman) who is steering
high - An area of high atmospheric pressure in a weather system
high tide - High water, the highest level reached
hitch - A knot attaching a line to an object, such as a cleat, ring, spar
holding tank - Storage tank for sewage, so that it will not be pumped overboard into the water
homing - Steering directly toward a radiobeacon or other source of radio signals, using a direction finder
horizontal angle - An angle, usually measured with a sextant, between two landmarks, providing a line of position (the arc of a circle)
horseshoe buoy - A lifebuoy or Personal Floatation Device, used in rescues, shaped like an inverted U and mounted in a bracket at the rail; used for crew-overboard situations
hull - The structural body of a vessel, not including superstructure, masts or rigging
hurricane - A tropical revolving storm of high intensity (Force 12 in the Beaufort scale); this term is used in the North Atlantic and the Caribbean; the same kind of storm in the Pacific is called a typhoon; inland it is a cyclone
hydrofoil - A type of boat with underwater foils on which the boat rides (planes) when high speeds are reached
hydrography - The science of surveying the waters of the earth
I
inboard - More toward the center of a vessel; inside; a motor fitted inside a boat
inboard cruiser - Powerboat with an inboard engine
inflatable - Craft that has an inflatable structure
Inland Rules - Rules of the road for for vessel operations in harbors, and certain rivers, lakes and inland water ways
inlet - A narrow area of water extending inland from a large offshore body, such as the ocean, often connecting with an interior body, such as a bay or river
Intracoastal Waterways - ICW: bays, rivers and canals along coasts (such as Atlantic and Gulf of Mexico coasts), connected so vessels may travel without entering open sea
irons, in - Up in the wind and unable to pay off on either tack. A sailboat that loses headway (and therefore steerageway) when attempting to come about is said to be "in irons" or "in stays"
isobars - On a weather map, lines drawn connecting places of equal atmospheric pressure; isobars close together indicate a steeper gradient of pressure and stronger winds
isogonic lines - Lines, on a chart, connecting points of equal magnetic variation
J
Jacob's ladder - A rope ladder, lowered from the deck, as when pilots or passengers come aboard
jetty - A structure, usually masonry, projecting out from the shore; a jetty may protect a harbor entrance
jib - A triangular sail, set on the headstay
jibe - To change direction, when sailing with the wind aft, so that the wind comes on a different quarter and the boom swings over to the other side; an actual jibe can be dangerous
jiffy reefing - A reef that is tied in
K
keel - The main structural member of a vessel, the backbone; the lateral area beneath the hull to provide stability and reduce leeway
ketch - A two-masted sailing rig; the after (mizzen) mast is shorter than the forward (main) mast and stepped forward of the rudder post, so the mizzen sail on a catch is relatively larger than it might be on a yawl
king plank - The center plank on a laid deck
kink spoke - The topmost spoke of a steering wheel when the rudder is in a centered position
knees - Structural members connecting (and reinforcing) two parts that meet, as the sternpost to the keel
knot - (1) Unit of speed, one nautical mile per hour; (2) a general term for a hitch or a bend
L
laid up - Not in commission and ready for use
lapstrake - A type of hull construction in which each strake (plank) overlies the next one below, also called clinker-built
latitude - Geographic distance north or south of the equator, measured in degrees, minutes and seconds or fractions of a minute
launch - (1) To move a boat into the water from land; (2) a powerboat used as a ferry between land and a moored boat; also "shore boat"
lay - The twist of a standard rope, usually to the right
lazarette - A small storage compartment at the stern
lead - A shaped weight on a marked line, used to measure water depth and to pick up bottom samples (mud, clay, sand)
lead line, hand lead - A weight, attached to a line, lowered into the water to find out the depth
lee - The direction toward which the wind blows; an object sheltered in the wind is "in the lee." A lee shore is the coast lying in the direction toward which the wind is blowing
leeboards - Anti-drift boards attached to the gunwale
leech - Trailing edge of a sail
lee helm - The tenancy of a sailboat to turn the bow to leeward, compared to weather helm, unless corrective rudder action is taken
leeward - Toward the lee
leeway - Sideways drift of a boat, primarily caused by the wind or a current
left-hand lay - Stranded rope made with a twist to the left; also called S-twist; most rope is right-hand lay, or Z-twist
length overall (LOA) The distance between the tip of the bow and the end of the stern
lifelines - Lines usually of wire rope, often covered with plastic, at the sides of a boats deck to keep persons from falling overboard
life preserver - A floatation coat, vest, ring or cushion; called Personal Floatation Device (PFD) in the U.S.
life raft - A small survival craft, usually inflatable
lights - Lighthouses or beacons; fixed aids to navigation that are equipped with light sources having certain prescribed characteristics
limber holes - Drainage holes in the bilge timbers of a vessel, allowing water to run to a low point for pumping out
line - A rope in use aboard a vessel; laid line is formed by twisting three (sometimes four) strands; braided line may be single or braid over a core
linestoppers - Also called jamcleats; they will keep the tension on the line while stopped or jammed
list - (1) A continuous leaning to one side, often caused by an imbalance of stowage or a leak into one compartment; (2) a Light List is a printed listing of aids to navigation, in geographical order
LOA - Length over all; the maximum length of a vessel's hull, excluding projecting spars or rudders
load waterline - LWL; the planned waterline of a boat, to which it is expected to float when fully loaded and equipped
locker - A stowage place, a closet
log - (1) A device measuring distance run through the water; (2) a written record, usually in a book, of a vessel's coarse, speed, weather encountered, radio transmissions and receptions, as well as other details of navigation and maintenance
longitude - Geographic distance east or west of the prime meridian (0º) which runs through Greenwich, England
long splice - A splice joining two rope ends, made by untwisting strands, thinning and removing the ends, so that the final splice is no thicker than the original line; a long splice will thus go through a block without jamming, but it is not as strong as a short splice
lubber's line - The index mark, usually inside the compass, by which the coarse is read and the vessel is steered
luff - The forward part or leading edge of a sail
LWL - Length on the waterline; the length of a vessel - including rudder post - when measured at the line of floatation
M
magnetic course - Course of a vessel related to magnetic north
magnetic meridian - A line of horizontal magnetic force of the Earth to which the compass, in the absence of deviation, aligns itself
magnetic north - The direction a compass needle points when there are no local disturbing influences (deviation)
mainsail - The sail hoisted on the after side of the main mast, pronounced "mans'l"
make fast - Action of attacking a line
manila - Natural fiber rope, largely supplanted by synthetics
marina - A place, essentially a dock area, where small recreational craft are kept; usually floats or piers, as well as service facilities, are available
marine railway - Railway used to haul out boats in a marina or boat yard
marline - Light two-stranded line (formally of hemp), tarred or untarred, used for lacing, whippings, seizings and serving
marlinespike - A pointed steel tool for splicing line
mast - A vertical spar, the main support of the sailing rig of sailboats and used for radio antennas and signal flags on both sail and power boats
masthead light - A white light, at or near the masthead, used underway by a vessel under power at night; the range of visibility required varies with the size of a vessel; the arc of visibility is from dead ahead to 22.5 degrees abaft the beam, on both sides
MAYDAY - A radio-telephone distress call, from the French m'aidez (help me)
meridian - A line passing through both poles and intersecting the equator at right angles, known as longitude. The prime meridian is that of Greenwich (0 degrees)
messenger - A light line used to carry another line such as a halyard or hawser from a ship to the shore or to another vessel
midships - Location near the center of a vessel measured either from side to side or fore-and-aft
mile - The statute mile is 5280 feet; the nautical mile is 6076.12 feet (1852 meters exactly); a knot, a measurement of speed, is one nautical mile per hour
mizzen mast - In a ketch or yawl, the aftermost mast; the mizzen sail is set on this mast
monkey fist - A special and fancy knot, used to weight the end of a heaving line
moored - Anchored, made fast to a pier, wharf, etc.
Morse code - A communication code invented by Samuel Morse, originally for the land telegraph; the code, modified for radio use, uses dots and dashes for letters, numerals and a few special signs
motorboat - A boat propelled by an internal combustion engine; the United States Power Boat Act divides motorboats into for classes based on length
motor sailers - An auxiliary sailboat with an especially large engine and spacious accommodations
mouse, mousing - Turns of twine, taken across a hook, to prevent accidental unhooking
multihull - Any of several boat designs with more than one hull, as a catamaran or a trimaran
mushroom anchor - Generally a mooring type of anchor, desirable because it will not snag an anchor line or chain; small mushrooms are also used for fishing anchors or for prams and dinghies
N
Napier diagram - A graphic plot of compass deviation values
Nautical Almanac - An annual publication, issued issued jointly by the U.S. Naval Observatory and H.M. Nautical Almanac Office at Greenwich, England, containing tables of the positions and movements of celestial bodies
nautical mile - 6076.12 feet (1852 m), an international standard; for practical purposes, equals one minute of latitude
naval architect - Architect specializing in marine design
navigation - The art/science of determining a vessel's position and guiding it safely and efficiently to another position; coastal navigation, using visual (surface) reference points, is more usually called piloting; celestial navigation uses observation of heavenly bodies (usually with instruments) and tables or calculators; radio navigation is the technical term when electronic devices and systems are used
navigation lights - Light shown by a vessel that indicate course, position and status such as fishing or towing
Navigation Rules - The Rules of the Road in the U.S., governing navigation lights, rules for vessels meeting or passing, sound signals, and distress signals; the rules for International and U.S. waters differ in only a few small details
neap tide - One occurring when the sun and moon are farthest from being in line (quarter and three-quarter moons); neap tides have the least range (rise and fall)
net tonnage - A vessel's capacity, determined by measuring its hull interior and subtracting the volume of non-cargo spaces (engine room, crew quarters, etc.)
non-slip - Anti skid
Notice to Mariners - A publication of the Defense Mapping Agency with participation by the U.S. Coast Guard and National Ocean Service, concerning navigational safety items such as changes in channels and navigation aids; this information is useful for updating charts and technical publications; various notices are both national and local in scope
numbering - The federal mandated "licensing" of boats in the U.S., usually by the states, except in Alaska, where the Coast Guard registers boats
nun - A type of cylindrical buoy, tapering toward the top, used in the lateral system of aids to navigation; typically nun buoys are red and are identified with an even number
nylon - A polyamide synthetic material with a long chain molecule; nylon fibers are used for rope and and some sailcloth, when elasticity is desirable; hard nylon is used for some rigging parts, such as sheaves
O
oarlock - A U-shaped or sometimes O-shaped pivoting device in which oars are set when rowing
offshore - (1) out of sight of land; (2) from the land; toward the water
Omega navigation system - A global radionavigation system (now largely obsolete)
outboard - (1) A propulsion unit for boats, attached at the transom; includes motor, driveshaft and propeller; fuel tank and battery may be integral or could be installed separately in the boat; (2) outside or away from a vessel's hull; opposite of inboard
outdrive - A propulsion system for boats, with an inboard motor operating an exterior drive, with driveshaft, gears and propeller; also called stern drive and inboard/outboard
outhaul - A line, tackle or geared mechanism used to tighten or adjust the foot of a sail on a boom
overall length - The extreme length of a vessel, excluding spars or rigging fittings
P
painter - A towline or tie-up line for a small boat
palm - The broad tip of an anchor fluke; a device, usually leather, worn on the hand and used somewhat like a thimble for sewing on canvas and for whipping lines
parallax error - The error in reading an instrument such as a compass or gage from off to one side, resulting from the distance between the needle or pointer and the numerical scale
parallel rulers - A navigation device, used in chartwork, that enables a person plotting a course to work from a piloted line on a chart to a compass rose, and vise versa, to determine the direction of the line,
plot a bearing, etc. It consists of two rulers of equal length, connected by crosspieces of equal length, moveable about the joints so as to keep the rulers parallel to each other even when moved across the chart
parcel - To wrap tape or or other small stuff around a wire or fiber rope, to prevent chafe; usually used with "worming" that fills in the spaces between the twisted strands of rope
passage - One leg of a voyage; a journey
patent log - A device, including rotor on a towline and counter, for measuring distance run and speed
pay out - To release line in a controlled manner, as with an anchor rode
pedestal - Base upon which is mounted the wheel or helm
pelorus - A sighting device, without a compass, used to determine relative bearings
pennant - (1) A small flag, typically a signal flag; (2) a short length of line or cable between a mooring chain and the boat, sometimes called a pendant
personal floatation device - A PFD is any of several articles such as buoyant cushions and vests or coats, "horseshoes" or life preserver rings
PFD - U.S. official terminology for life preserver; personal floatation device
pier - A structure, usually wood or masonry, extending into the water, used as a landing place for boats and ships
pile, piling - A vertical wooden, concrete or metal pole, driven into the bottom; may be a support for a pier or floats or an aid to navigation; also used for mooring
piloting - Navigation using visual reference points (aids to navigation, landmarks, etc.) and water depths
pitch - (1) The alternating rise and fall of the bow of a vessel proceeding through waves; (2) the theoretical distance advanced by a propeller in one relolution; (3) tar and resin used for caulking between the planks of a wooden vessel
planing hull - A hull designed so that forward speed creates water lift, reducing friction and increasing speed
planking - Lengths of wood used for the external skin or the deck of a vessel
Pleasure Vessel License - A form of USCG documentation that does not allow commercial use
plumb bow - Hull with vertical bow shape
polyester - Synthetic material (typical trade name, Dacron) used for fibers for rope and sailcloth; polyester is stronger and has less elasticity than nylon
polypropylene - Lightweight synthetic material used for cordage fibers, for ski tow ropes, dinghy painters and other uses where floatation is desirable; not as strong as other synthetics, the fibers are sometimes combined with others for special purposes
port - (1) Left, as the port side of a boat, or a direction, as to "turn to port"; (2) an opening, for light and/or ventilation, in the side of a vessel; (3) general area of a shore establishment having facilities for landing and maintaining vessels
port tack - A sailing vessel with the wind coming from the left, or port, side is said to be on the port tack; such a vessel normally does not have the right of way when meeting a vessel on the starboard tack
position finding - The navigation process of determining the position of a vessel on a chart or in the water
pram - A small oat used as a tender; a dinghy in the U.S., usually with a squared-off bow
prevailing winds - Usual direction of a wind
prime meridian - The meridian of longitude through Greenwich, 0º
privileged vessel - One having the right of way, as to both course and speed, when meeting another vessel
propeller - A rotating device, with two or more blades, that acts as a screw in propelling a vessel
protractor - Navigational device used in chartwork to measure and lay down angles
psychrometer - A weather instrument, usually two hygrometers, one dry and one with a wet bulb, to measure the moisture in the air
pulpit - The forward railing structure at the bow of a boat
pump out - Action of pumping out waist tank
purchase - A mechanical device for lifting or pulling; on shipboard the term is used specifically for a block and tackle
Q
quarter - The side of a vessel, from amidships to the stern
quartering sea - Seas coming from the quarter
quay - A masonry structure at the water's edge, where vessels can tie up, load and unload cargo
R
radar - An electric system using super high frequency radio waves; when reflected they show on a screen the position, size and distance of an object; radar is used at night and in bad visibility for both collision avoidance and navigation.
radar arch - Supporting structure for radar that is shaped as an arch
radiobeacon - A transmitter, at a fixed and known location, used by vessels with appropriate electronic equipment to determine their position (see 'radio direction finder').
radio bearing - A direction determined by radio
radio direction finder - A radio receiver with special antenna and circuitry used to determine the direction to a source of radio waves.
radionavigation - Electronic piloting; the determination of a vessel's position, course and speed by various electronic devices and systems.
rafting, rafted - The mooring procedure for two or more vessels, tied up side-by-side at a dock or on an anchor.
rail - A protective edge on a deck; also a solid bar on supports, similar to a lifeline.
raised deck - Deck level arranged to be higher than the actual gunwale.
rake - (1) The slant of a a ship's funnels, bow or stern; (2) the slant, fore and aft of a mast.
RDF - Radio direction finder, an electronic device used in conjunction with transmitters, in order to determine a vessel's position.
reach (reaching) - (1) To sail across the wind; (2) a channel between the mainland and an island.
reciprocal - A direction precisely opposite another; differing by 180 degrees.
reef - (1) An underwater barrier, such as a rock or coral; (2) the shorten sail by reducing the area exposed, by rolling the sail on a boom or tying in reef points.
reef knot - The knot used to tie in a reef; a square knot, also useful for tying around an object, but not good for fastening two lines together.
reef points - Tie lines, placed at intervals horizontally on a sail, used to reduce sail area when they are tied around the foot of the sail.
reeving - Leading a line through a block or fairlead as in setting up a purchase, or rigging a halyard.
registration - the numbering or licensing of a boat
relative bearing - A direction in relation to the fore-and-aft line of a vessel, expressed in degrees.
rhumb line - A straight line on a Mercator chart; it intersects all meridians at the same angle; for short distances a rhumb line provides an adequate course, but a great circle is actually the shorter distance.
reverse sheer - Sheer the reverse of normal. The sheerline rises above the straight line from stern to stern instead of curving below.
RIB - See rigid inflatable.
ribs - Another term for 'frames,' the transverse members of a wooden hull to which the planks are fastened.
riding light - The anchor light.
rig (rigs) - (1) The spars, standing rigging and sails; (2) to make a boat ready for sailing or to prepare a sail or piece of gear for use.
rigging - The wire rope, rods, lines, hardware and other equipment that support and control the spars and sails; standing rigging is semi-permanent once set up; running rigging is continually adjusted as the sails are hoisted, doused, trimmed or reefed.
right-hand lay - The twist of stranded rope commonly used, with the strands twisting to the right; Z-twist.
right of way - In both normal boat operation and racing, certain boats (privileged or stand-on vessels) have priority in crossing or overtaking situations, or at turns in races; the other craft (burdened or give-way vessel) must yield to the boat that has right of way in a particular situation; the boat on starboard tack, or the vessel coming from the right in the case of power boats, will have the right of way under most conditions.
rigid inflatable - Inflatable boat with a rigid bottom.
rode - The anchor line, which may be line (fiber rope), chain or wire rope.
roll - The alternating motion of a boat, leaning alternately to port and starboard; the motion of a boat about its fore-and-aft axes.
roller furling - The method of furling a sail by winding it on a stay, most used for jibs but used for mainsails on some cruising boats.
roller reefing - Reduction of sail area by winding the sail on a rotating boom.
rolling hitch - A knot used for attaching a line to another line or to a spar.
rope - Cordage, lines made of fiber or steel; rope may be braided or formed with twisted strands; when in use aboard ship it is generally called line.
round turn - A turn, of line, around an object or a line; part of a knot.
rowlock - See 'oarlock'.
rub rail, strake or guard - an outer member on the side of a vessel's hull, designed to absorb friction and pounding from contact with pilings, docks, etc.
rudder - The control surface, usually aft, by which a boat is steered.
rudder post - The shaft that carries the rudder and to which the tiller and wheel is connected.
rules of the road - A general term for the regulations governing vessels, used to prevent collisions; in the U.S. the technical name is now Navigation Rules; the rules vary slightly inland and in international waters, but are generally similar.
running fix - A navigation fix obtained by using a line of position taken at or near the current time together with another or earlier LOP that has been advanced for the movement of the vessel between these two times.
running lights - The required lights, called Navigation Lights, that a vessel shows at night or in poor visibility, to indicate position, course and status.
running rigging - The adjustable lines (and certain hardware items) used for the control of spars and sails.
S
safety harness - Harness with webbing used with a safety line to lessen chances of persons on deck falling overboard.
samson post - In a small vessel, a single bitt forward used to fasten the anchor and dock lines; in larger vessels the term is applied to a small forward derrick mast, used with a cargo boom.
satellite navigation - A form of position finding using radio transmissions from satellites with sophisticated on-board automatic equipment.
schooner - A fore-and-aft rigged sailing vessel with two or more masts, with the foremast shorter than the mainmast.
scope - Technically, the ratio of length of anchor rodein use to the vertical distance from the bow of the vessel to the bottom of the water; generally, the amount of cable anchor in use; a minimum scope of four to one is normal good conditions, increasing to as much as ten to one in bad storms.
screw - A propeller; sometimes called a wheel.
scudding - Running before the wind in a gale.
scuppers - Drain holes on deck; in the toe rail, or in bulwarks or (with drain pipes) in the deck itself.
scuttlebutt - Gossip, rumors, so called because sailers used to gather around the scuttlebutt, a cask for drinking water.
sea anchor - Canvas shaped like a parachute or a cone with an opening at the tip to keep a boat's bow to the seas in open water and reduce drift to a minimum; not a means of anchoring.
sea cock - A through-hull fitting with a valve that can shut off the flow of water between the boats interior and exterior.
seakindly - Comfortable in rough seas, moving through the water without undue motion or strain; said of vessel's hull design.
seamanship - All the arts and skills of boat handeling, ranging from maintenance and repairs to steering, anchoring, docking, sail handling, marlinespike work and rigging.
seiche - An oscillation of the surface of a lake or landlocked sea that varies in a period from a few minutes to several hours.
seizing - Binding two lines together, or a rope to a spar and so on, using light line.
self-draining - Drains automatically.
sentinel - Weight suspended from the rode to help keep the puill on the anchor as horizontal as possible to prevent dragging in rough water.
serving - Covering and protecting a portion of a line, to prevent wear; a serving may be as simple as a whipping (small stuff wrapped around) or more elaborate, with worming, parcelling and the addition of waterproofing.
set (e.g. sails are set out) - (1) To raise a sail; (2) the direction of a current.
sextant - A precision navigating instrument, used for measuring angles, as in celestial navigation when the altitudes of heavenly bodies are taken, or in piloting, when the known heights of objects ashore or the known distance of two objects from each other can be used to find distance.
shackle - A metal link fitting with a pin across the throat, used to connect lines to an anchor, fasten blocks to a spar in rigging, or a line to a sail.
shear pin - A safety device, used to fasten a propeller to its shaft; it breaks when the propeller hits a solid object, thus preventing further damage.
sheave - A grooved wheel or pully over which rope or rigging wire runs, used to change the direction of force; often sheaves are part of blocks.
sheer - (1) The curvature of the deck, fore and aft, as seen from the side; (2) a turn off course, from poor helmsmanship or difficult steering; (3) a swing, as on a moored boat.
sheerstrake - The topmost plank on the side of a wooden planked boat; the one that shows the sheer of the deck.
sheet - A line used to control a sail's lateral movement, either directly or by limiting the movement of a boom or other spar.
sheet bend - A knot useful for bending a line to an eye or to join two lines of different sizes.
ship - (1) A large seagoing vessel; (2) a three-masted sailing vessel with square sails, called "full-rigged," on each mast; (3) to take something aboard, as water in rough seas; (4) to place gear in place, as to ship a rudder or to ship oars, to bring them inboard when not in use.
shipshape - In good order, in good condition, properly rigged and ready.
shock cord - An elastic "rope" originally developed for aviation, useful in limited rigging or stowage situations.
short splice - A quick splice, as the end of two lines together, that is moderately strong but will not always run through a block or fairlead, because of its bulk. (see long splice).
shrouds - Fixed rigging on either side of the mast.
sidelights - Red and green navigation lights, visible from forward or on the beam. (see running lights).
signal halyard - Halyard for hoisting the signal flags and pennants.
slack - (1) Not moving; (2) loose; (3) to ease.
slack water - The period of little or no water movement between flood and ebb tidal currents.
sliding hatch - Hatch mounted on sides.
slip - (1) A birth for a boat between two piers or floats or piles; (2) the percentage difference between the theoretical and the actual distance that a propeller advances when turning in water under load.
small stuff - Cordage such as marline, spun yarn, sail twine, primarily used for whippings and servings.
snub a line - To check a running rope quickly, usually by tension around a bitt or cleat.
sole - The cabin or cockpit floor.
soundings - Measurements of the depth of water as shown on a chart; a vessel is "off soundings" if it is in water too deep to use a long (deep sea) lead line; inside the 100 fathom line is usually "on soundings."
spars - Masts, booms, gaffs and poles used in sailboat rigging; today spars are made of wood, aluminum extrusions, and composites of synthetics.
spinnaker - A three-cornered sail of light, stretchy cloth, usually nylon, used in downwind sailing.
splice - To join two lines, or make an eye, by tucking strands or otherwise interweaving parts of a rope; braided rope that has a core a a cover is usually spliced by tucking one side inside the other.
spoon bow - A full round bow that is shaped like the bowl of a spoon.
spring line - One of the standard dock lines, used to cotrol fore and aft motion of a boat made fast to a peir or float.
spring tide - One that occurs when there is a new moon, with the sun and moon inconjunction, or when there is a full moon, the moon and sun being in opposition,; at such times, high tides are higher than normal, and low tides are lower; the tidal range is greater. (see neap tide).
squall - A sudden and violent wind storm often accompanied by rain; a line squall or line of squalls quite often accompanies a cold front.
square knot - Another name for the reef knot, usefull for tying two ends a of a line together, as around an object; not a good knot to use when fastening two lineswhere the strain will be intermittent.
square rigged - Vessel rigged with sails that are hung laterally and of square shape.
stanchion - A metal post, used to hold lifelines along a deck.
stand - Period of time when vertical rise or fall of the tide has stopped.
standing part - The portion of a line not used in making a knot, or the part of a line around which the knot may be tied; in a block and tackle, the part of the purchase that deoes not move when power is applied to the hauling part.
standing rigging - The permanent says and shrouds, as well as some other rigging parts, used mainly to hold up the mast and take the strain of the sails; although necessarily somewhat adjustable the standing rigging is not continually changed as the running rigging.
stand-on vessel - The boat that has the right of way in a crossing or overtaking situation; the privilaged vessel. (see give-way vessel).
starboard tack - A vessel standing with the wind coming over the starboard side is on the starboard tak and generally has the right of way over a boat on the port tack.
stateroom - Sleeping quarters for guests or captain.
statute mile - A unit of measurement on land and most inland waters, 5280 feet; (see nautical mile).
stays - Rigging, generally wire or rods, used to support the masts in a fore-and-aft direction and to carry certain sails.
staysail - An additional foresail that is set between the mast and the jib.
steerageway - Sufficient motion through the water to enable a vessel to respond to its rudder.
stem - The forward memebr of the hull, or the corresponding portion of the hull in composite construction.
step - At the base of the mast, the special part of the boat in which the heel of the mast is set; to raise the mast and put it in place.
stepped - Referring to the mast, keel stepped or deck stepped.
stern - The after portion of the boat.
stern drive - An inboard/outboard engine system, with the motor inside the hull; steering is done by turning the outboard (propeller) unit.
stern line - The dock or mooring line that runs from the stern to the peir, float or pile.
sternway - Opposite of headway; having a reverse motion through the water.
stores - Supplies.
storm jib - A small, strong, triangular headsail that is used in heavy winds.
stow - To put in the proper places.
strakes - Lines of planking, as from stern to stern. (see sheer strake and garboard strake).
stuffing box - A though-hull fitting for the drive shaft or rudder post, also called a gland.
suit of sails - The full compliment of a boat's sails.
superstructure - Cabins and other structures above deck.
surf - Waves breaking on a shore, reef or bar.
survey - Inspection for purposes of purchase or insurance by a marine surveyor.
surveyor - A profesional who surveys (examines boats and ships) for insurance purposes or prior ro a purchase.
swamp - To fill with water, not from a leak but from water coming over the deck and gunwales.
swell - A long, large wave that does not crest; swells come from such a distance that the wind causing them is not apparent locally.
swim platform - Platform installed at the transom for ease of boarding.
T
tachometer - An instrument that indicates an engine's revolutions per minute.
tack - The forward bottom corner of a sail, or either bottom corner of a square sail; each leg of a zigzag course sailed to windward or downwind.
tacking - The sailing amneuver in which the direction of the boat is changed, often with rigging adjustments, so that the wind is coming from the other side of the vessel.
tackle - A purchase, a block and tackle, a combination rig of one or more blocks with lines to obtain mechanical advantage.
tack rag - A slightly sticky cloth used to pick up dust and dirt from brightwork before varnishing.
telltale - A wind-direction indicator, mounted on the rigging, sail or mast.
tender - A small boat accompanying a yacht or other pleasure vessel, used to transport persons, gear and supplies; a dinghy; a vessel is said to be tender if it is relatively unstabel.
tensile strength - The load, in pounds of "pull," at which a rope, chain or other item would break.
thimble - Metal fitting used in rigging, forming a reinforced place of attachment.
throat - The forward upper corner of a four-sided fore-and-aft sail, the point where the throat halyard attaches.
thwart - A crossways seat, usually contributing to the structure strength in a rowboat or other small open boat.
tidal current - Regular current caused by the rise and fall of the tides. (see current).
tides - The vertical rise and fall of ocean water, and waters affected by the ocean, caused by the gravitational forces of the moon and sun.
tide tables - A set of data giving the times and heights of high and low tides for one or more locations.
tiller - An arm or lever attached to the top of a rudder post for the pupose of controling the position of the rudder and so steering the craft.
toe rail - The low bulwark on a small decked boat.
tonnage - A measure of the capacity or displacement of a vessel. (see gross tonnage, net tonnage).
topping lift - A running rigging line to control a spar; typically an adjustable topping lift would run over a sheave or through a block at the top of the mast down to the end of a boom or spinnaker pole.
topsides - (1) The sides of a vessel above the water line; (2) on deck as opposed to below deck.
towing - Pulling a vessel through the water, as a towboat pulls a barge or a yacht club tender pulls one or more racing sailboats; an assistance or rescue maneuver.
track - (1) Metal or plastic rigging fitting, used to control spars, blocks and other rigging parts; (2) the path, normally shown on a chart, between one position and another, as a dead reckoning track.
traffic separation scheme - A plan, generally internationally aggreed on, by which vessels in congested areas use one-way lanes to lessen the dangers of collision.
transom - The transverse part of the stern.
trim, trimmed - (1) The way in which a vessel floats, on an even keel, or trimmed by the head (bow) or stern, for example; adjustable by shifting ballast; (2) to set sails, to adjust by means of sheets and certain other rigging lines.
trimaran - A boat with three hulls.
trip line - A line fast to the crown of an anchor by means of which it can be hauled out when dug too deaply or fouled; a similar line used on a sea anchor to bring it aboard.
trough - Depression between two waves. (see crest).
true course - A course corrected for variation and deviation; one that is referenced to geographic north.
true north - Geographic north.
true wind - The actual direction and force of the wind, as distinct from from apparent wind, which varies with the speed and directionof the vessel.
tumblehome - The inward curving of the topsides, above the water line.
tune - To adjust the rigging and sails for maximum efficiency; the term is also used for engine adjustments.
tunnel hull - Hull with tunnels shaped for the propeller to reduce draft.
turnbuckle - A threaded, adjustable rigging fitting, used for stays, lifelines and sometimes other rigging.
turning circle - The course followed by a boat when it is turning; the smallest possible circle when the rudder is hard over.
twine - Small stuff, light line used for whippings or servings; sail twine used for sewing.
two-blocked - Fully closed up, raised as far as the gear permits, as when both blocks in a purchase are drawn completely together.
two half-hitches - A useful knot, in which the hitches are made upon the standing part of the line and then drawn up (tightened).
U
underway - A vessel not at anchor or aground or made fast to the shore.
Underwriters Laboratories - One of the chief testing organizations that helps to set the safety standards used in the United States.
upwind - To the windward of.
USCG - United States Coast Guard. The federal marine law enforcement and rescue agency in the US.
USPS - United States Power Squadrons, a private membership organization that specializes in boating education and good boating practices.
V
V-drive - Mechanism used with an engine installation that has the normally aft-facing end of the engine facing forward.
V-hull - Hull shaped in a V.
variation - A compass "error" resulting from the fact that at most points on the earth's surface the direction of the magnetic lines of force is not toward the geographic north pole of south pole.
vector - A line drawn to represent magnitude and direction, such as leeway a boat makes in a given time period as a result of wind or water current.
veer - To change direction, to swerve; to veer out is to let out rope, as an anchor line; when the wind veers it changes direction clockwise, as opposed to backing (counterclockwise).
vent - An opening ina boat's ventalation system.
ventilators - Openings that are fitted with cowls (scoops) to direct the flow of air and vapors in and out of ducts.
vessel - A boat, ship or other moving and floating craft; a barge is a vessel, a float at a peir is not a vessel.
VHF radio - A Very High Frequency electronic communications system.
voyage - A complete trip, as distinguished from a passage.
W
wake - The track in the water of a moving vessel; commonly used for the distubance of water (waves) resulting from the passage of the vessel's hull.
wash - The loose or broken water left behind a vessel as it moves along; the surging action of waves.
water ballast - Ballast in the form of water in the tanks.
waterline - The intersection of a vessel's hull and the water's surface; the line separating bottom paint and topsides.
waves - Undulations of the sea; the height of a wave is measured from trough to crest; the length is the distance between crests; the period is the time between two successive crests.
weather helm - The tendancy of a vessel to turn to waindward, requiring a slight amount of helm to keep it on course; normally this is considered a sailboat safety element.
weather shore - The coast lying in the direction from which the wind is blowing, as opposed to a lee shore. (see lee).
weather side - Side of a boat upon which the wind is blowing.
weigh - To raise the anchor, to depart.
well-found - With adequate equipment and stores, well supplied and fitted out.
wetted surface - The area of the wetted part of a hull (including rudder) in the water, affecting speed.
wharf - A structure, parallel to the shore, for docking vessels.
wheel - (1) the steering wheel; (2) the propeller.
whipping - Twine wound around a line, as on the end or at an ey splice, to add strength and prevent fraying or abrasion.
whistle signal - A standard communication signal between boats, to indicate change of course, danger or other situations.
winch - A device, on deck, on a spar or otherwise mounted, which is used to haul on a line; if geared or used with a handle (lever) it provides a mechanical advantage.
windage - Wind resistance.
windlass - A special form of winch, a rotating drum device for hauling a line or chain.
windward - The direction from which the wind is blowing.
workboat - A small vessel or boat used for such chores as ferrying stores or putting down moorings.
working sails - The sails used in normal winds, as distinguished from light weather sails or storm sails.
worm - To fill in the spaces in laid rope, as part of the procedure known as worm-and-parcel.
X
Y
yacht - A pleasure vessel, a pleasure boat; in American usage the idea of size and luxury is conveyed, either sail or power.
yard - (1) A spar, crossing the mast, on which square sails are fitted; (2) a place where boats are stored, constructed, or repaired.
yaw - To swing or steer off course, as when running with a quartering sea.
yawl - A rig for two-masted sailboats, in which there is a mainmast and a smaller mizzen mast, stepped aft of the rudder post.
Z