Glossary of Nautical Terms & Abbreviations

Nautical terms might sound like a foreign language to beginners, but they stand in a proud tradition. They are often practical and will definitely add to your self confidence once they became part of you own repertoire. On this page, you can learn to talk like a sailor - but don't forget that it takes more than words to run a boat.

There are printable downloads available at the end of each section, for you to print or save to your desktop. These will aid your revision for the Self Test Area.

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  • Aback  - describes a sail when the wind strikes it on it's lee side.
  • Abaft   - towards the boats stern.
  • Abeam   - at right angles to the centre-line of the boat.
  • Aft   - at or near the stern.
  • A-hull   - to ride out a storm with no sails set and the helm lashed to leeward
  • AIS   - Automatic Identification System
  • Amidships   - the centre of the boat, athwartships and fore-and-aft
  • Apparent wind   - the direction and speed of the wind felt by the crew, it is a combination of true wind and that created by the movement of the boat.
  • ARPA   - Automatic Radar Plotting Aid
  • Astern   - behind the boat; to go astern is to drive the boat in reverse.
  • Athwartships   - at right angles to the fore-and-aft line of the boat.
  • Azimuth   - angular distance measured on a horizon circle in a clockwise direction, usually between an observer and a heavenly body



  • Back    when a wind backs, it shifts anti-clockwise.
  • Back a sail    to sheet it to windward so that the wind fills it on the side that is normally to leeward.
  • Backstay   a stay that supports the mast from aft and prevents its forward movement.
  • Baggywrinkle   rope, teased out, plaited together and wound around stays, shrouds etc. to prevent chaffing.
  • Ballast    extra weight, usually lead or iron, placed low in the boat or externally on the keel to provide stability.
  • Ballast keel    a mass of ballast bolted to the keel to increase stability and prevent the boat from capsizing.
  • Batten    a light, flexible strip, fed into a batten pocket at the leech of the sail to support the roach.
  • Beam  (1) the maximum breadth of the boat, (2) a transverse member which supports the deck, (3) on the beam, an object is at right angles to the centre-line.
  • Bear away   to steer the boat away from the wind.
  • Bearing    the direction of an object from an observer, measured in degrees true or magnetic.
  • Beat   to sail a zigzag course towards the wind, close-hauled on alternate tacks.
  • Belay  to make fast a rope around a cleat usually with a figure of eight knot.
  • Bend  (1) secure a sail to a spar before hoisting, (2) connect two ropes with a knot.
  • Berth  (1) place occupied by a boat in harbour, (2) sleeping place on board.
  • Bight  a bend or loop in a rope.
  • Bilge  the lower, round part inside the hull where water collects.
  • Block  a pulley in a wooden or plastic case, consisting of a sheave around which a rope runs. It is used to change the direction of pull.
  • Boot-topping  a narrow coloured stripe painted between the bottom paint and topside enamel.
  • Broach  when a boat running downwind slews broadside to the wind and heels dangerously. It is caused by heavy following seas or helmsman' error.
  • Broad reach   the point of sailing between a beam reach and a run when the wind blows over the quarter.
  • Bulkhead  partition wall in a boat normally fitted athwartships.



  • Cable  distance of measurement equalling 0.1 sea mile, 185 metres, 200 yards
  • Centre-board   a board lowered through a slot in the keel to reduce leeway.
  • Centre-line  centre of the boat in a fore-and-aft line.
  • Chart Datum  reference level on a chart below which the tide is unlikely to fall. Sounding are given below chart datum. Datum level varies on country & area.
  • Claw ring   a fitting, which slips over the boom like a claw, to which the main sheet is attached after reefing the sail.
  • Cleat   a wooden, metal or plastic fitting around which a rope is secured.
  • Clew   the after, lower corner of a sail where the foot and leech meet.
  • Close-hauled   the point of sailing closest to the wind; see also beat.
  • Close reach   the point of sailing between close-hauled and a beam reach, when the wind blows forward of the beam.
  • Close-winded   describes a boat able to sail very close to the wind.
  • Course   the direction in which a vessel is steered, usually given in degrees, true, magnetic or compass.
  • Cringle   (1) a rope loop found at either end of a line of reef points, (2) an eye in a sail.



  • Dead run   running with the wind blowing exactly aft, in line with the centre-line.
  • Deviation   the difference between the direction indicated by the compass needle and the magnetic meridian, caused by metal objects aboard.
  • Displacement   (1) the weight of water displaced by a boat is equal to the weight of the boat;
  • Displacement   (2) a displacement hull displaces its weight in water & is only supported by buoyancy.
  • Downhaul   a rope fitted to pull down a sail or spar.
  • Draft   the vertical distance from the waterline to the lowest point of the keel.
  • Drift   (1) to float with the current or wind, (2) the distance a boat is carried by a current in a given time.
  • Drogue   a sea anchor put over the stern of a boat or liferaft to retard drift.
  • Drop keel   a retractable keel which can be drawn into the hull.



  • EPIRB  Emergency Position Indication Radio Beacon


  • Fairlead - a fitting through which a line is run to alter the direction of the lead of the line.
  • Fathom - the measurement used for depths of water and lengths of rope. 1 fathom = 6 ft = 1.83m
  • Fiddle - a raised border for a cabin table, chart table etc. to prevent objects falling off.
  • Fix - The position of a vessel as plotted from two or more position lines.
  • Forestay - the foremost stay running from the masthead to the stemhead, to which the mainsail is hanked.
  • Freeboard - vertical distance between the waterline and the top of the deck.



  • Genoa - a large headsail in various sizes, which overlaps the mainsail and is hoisted in light to fresh winds on all points of sailing.
  • Gimbals - two concentric rings, pivoted at right angles which keeps objects horizontal despite the boats motion.
  • GNSS - Global Navigation Satellite System
  • Go about - to turn the boat through the eye of the wind to change tack.
  • Gooseneck - the fitting attaching the boom to the mast, allowing it to move in all directions.
  • Goosewing - to boom out the headsail to windward on a run by using a whisker pole to hold the sail on the opposite side to the mainsail.
  • GPS - Global Positioning System
  • Guard rail - a metal rail fitted around the boat to prevent the crew from falling overboard.
  • Guy - a steadying rope for a spar a spinnaker guy controls the fore-and-aft position of the spinnaker pole; the foreguy holds the spinnaker pole forward.
  • Gybe - to change from one tack to another by turning the stern through the wind.



  • Halyard - rope used to hoist and lower sails.
  • Hank - fitting used to attach the luff of a sail to a stay.
  • HAT - Highest Astronomical Tide
  • Hatch - an opening in the deck giving access to the interior.
  • Head-to-wind - when the bows are pointing right into the wind.
  • Headfoil - a streamlined surround to a forestay, with a groove into which a headsail luff slides.
  • Heads - toilets.
  • Headway - the forward movement of a boat through the water.
  • Heave-to - to back the jib and lash the tiller to leeward used in heavy weather to encourage the boat to lie quietly and to reduce headway.
  • Heel - to lean over to one side.



  • IRPCS - International Regulations for Preventing Collisions at Sea
  • Isobars - lines on a weather map joining places of equal atmospheric pressure.
  • Jackstay - a line running fore-and-aft on both sides of the boat to which safety harnesses are clipped.
  • Jury - a temporary devices to replace lost or damaged gear.



  • Kedge - a small, light second anchor.
  • Keel - the main backbone of the boat to which a ballast keel is bolted or through which the centre-board passes.
  • Ketch - a two-masted sailing vessel with a mizzen mast slightly smaller than the main and stepped forward of the rudder stock/post.
  • Kicking strap - a line used to pull the boom down, to keep it horizontal, particularly on a reach or run.



  • Lanyard - a short line attached to one object, such as a knife, with which it is secured to another.
  • LAT - Lowest Astronomical Tide - Chart Datum
  • Leech - (1) the after edge of a triangular sail, (2) both side edges of a square sail.
  • Lee Helm - the tendency of a boat to bear away from the wind.
  • Lee shore - a shore onto which the wind is blowing.
  • Leeward - away from the wind, the direction to which the wind blows.
  • Leeway - the sideways movement off its course as a result of the wind blowing on one side of the sails and hull.
  • List - a boat's more or less permanent lean to one side, owing to improper distribution of weight.
  • Log - (1) an instrument for measuring a boats speed and distance travelled through the water. (2) to record in a book the details of a voyage.
  • Luff - The forward edge of a sail. To luff up is to turn the boat's head right into the wind.



  • Marinized engine   an auto engine which has been specially adapted for use in boats.
  • Mast step   the socket in the keel in which the base f the mast is located.
  • Measured mile   a distance of one nautical mile measured between buoys or transits/ranges ashore, and marked on the chart.
  • Meridian   an imaginary line encircling the Earth which passes through the poles and cuts at right angles through the Equator. All lines of longitude are meridians.
  • Mizzen   (1) the shorter after-mast on a ketch or yawl
  • Mizzen   (2) the fore-and-aft sail set on this mast.
  • MHWN   Mean High Water Neaps
  • MHWS   Mean High Water Springs
  • MLWN   Mean Low Water Neaps
  • MLWS   Mean Low Water Springs
  • MMSI  Maritime Mobile Service Identity



  • Outhaul MHWN   a rope used to pull out the foot of a sail.
  • Overall Length (LOA) MHWN   the boat's extreme length measured from the foremost part of the bow to the aftermost part of the stern excluding bowsprit, self-steering gear etc.



  • Painter   the bow line by which a dinghy, or tender is towed or made fast.
  • Pay out   to let a rope put gradually.
  • Point of sailing   the different angles from the wind on which a boat may sail, the boats course relative to the direction of the wind.
  • Port   the left hand side of the boat looking forward.
  • Port tack   a boat is on a port tack when the wind strikes the port side 1st & the main sail is out to starboard.
  • Position line/line of position   a line drawn on a chart as a result of taking a bearing along which a boat's position must lie. Two position lines give a fix.
  • Pulpit   a metal guard rail fitted at the bows of a boat to provide safety for the crew.
  • Pushpit   a metal guard rail fitted at the stern.


  • Quarter   the portion of the boat midway between the stern and the beam.



  • Range  (1) see transit.
  • Range  (2) of tides, the difference between the high and low water levels of a tide.
  • Range  (3) the distance at which a light can be seen.
  • Reach  to sail with the wind approximately on the beam , all sailing points between running and close hauled.
  • Reef  to reduce the sail area by folding or rolling surplus material on the boom or forestay.
  • Reefing pennant  strong line with which the luff or leech cringle is pulled down to the boom when reefing.
  • Rhumb line  a line cutting all meridians at the same angle, the course followed by a boat sailing in a fixed direction.
  • Riding sail  s small sail hoisted to enable a boat to maintain steerage way during a storm.
  • Rigging screw  a deck fitting with which the tension of standing rigging is adjusted.
  • Roach  the curved part of the leech of a sail which extends beyond the direct line from head to clew.
  • Run  to sail with the wind aft and with the sheets eased well out.
  • Running rigging  all the moving lines such as sheets and halyards used in the setting and trimming of sails.



  • Schooner   a boat with two or more masts with the mainmast aftermost.
  • Scuppers   holes in the toe rail which allow water to drain off the deck.
  • Seacock   a valve which shuts off an underwater inlet or outlet passing through the hull.
  • Sea room   room in which a boat can manoeuvre clear of land or other dangers.
  • Set   (1) to hoist a sail.
  • Set   (2) the way in which the sails fit.
  • Set   (3) the direction of a tidal current or stream.
  • Shackle   a metal link with a removable bolt across the open end, of various shapes D, U
  • Sheet   the rope attached to the clew of a sail or to the boom, enabled it to be controlled or trimmed.
  • Shrouds   ropes or wires usually in pairs, led from the mast to chain plates at deck level to prevent the mast falling sideways, part of the standing rigging.
  • Skin fitting   a through-hull fitting where there is a hole in the skin through which air or water passes. A seacock is fitted for when the hole is not in use.
  • Sloop   a single-masted sailing boat with one mainsail and one headsail.
  • Spar   a general term used for any wood or metal pole, e.g mast or boom, used to give shape to sails.
  • Spinnaker   a large, light balloon shaped sail used when reaching or running.
  • Splice   to join ropes or wires by unlaying the strands and interweaving them.
  • Spreaders   horizontal struts attached to the mast which extend to the shrouds and help support the mast.
  • Stall   a sail stalls when the airflow over it breaks up causing the boat to lose way.
  • Stanchion   upright metal post bolted to the deck to support the guard rails.
  • Standing part   the part of a line not used when making a knot, the part of a rope which is made fast or around which the knot is tied.
  • Standing rigging   the shrouds and stays which are permanently set up and support the mast.
  • Starboard   right-hand side of the boat looking forward.
  • Starboard tack   a boat is on a starboard tack when the wind strikes the starboard side first and the boom is out to port.
  • Stay   wire or rope which supports the mast in a fore-and-aft direction, part of the standing rigging.
  • Steerage way   a boat has steerage way when it has sufficient speed to allow it to be steered, or to answer the helm.
  • Sternway   the backward, stern-first movement of a boat.
  • Strop   a loop of wire or rope used to attach a block to a spar to make a sling.



  • Tack  (1) the lower forward corner of the sail.
  • Tack  (2) to turn the boat through the wind so that it blows on the opposite side of the sails.
  • Tacking  working to windward by sailing close-hauled on alternate courses so that the wind is first and one side then on the other.
  • Tang  a strong metal fitting by which standing rigging is attached to the mast or other spar.
  • Tender  or dinghy, a small boat used to ferry people and supplies from a yacht to shore.
  • Tide  the vertical rise and fall of the oceans caused principally by the gravitational attraction of the moon.
  • Toe rail  a low strip of wood or moulding running around the edge of the deck.
  • Topping lift  a line from the mast head to a spar normally the boom which is used to raise it.
  • Track  (1) the course a boat has made good.
  • Track  (2) a fitting on the mast or boom onto which the slide on a sail fit.
  • Track  (3) a fitting along which a traveller runs used to alter the tension of the sheets.
  • Trim  (1) to adjust the angle of the sails, by mean of sheets so that they work most efficiently.
  • Trim  (2) to adjust the boats load and thus the fore-and-aft angle at which it floats.
  • True wind  the direction and speed of the wind felt when stationary at anchor or on land.
  • Turn buckle  used to tighten the standing rigging.


U / V

  • Underway  a boat is underway when it is not made fast to the shore, at anchor or aground.
  • Up haul  is a line to raise something vertically for example the spinnaker pole.
  • Vang  see kicking strap
  • Veer   (1) the wind veers when it shifts in a clockwise direction
  • Veer  (2) to pay out anchor cable or rope in a gradual controlled way.



  • Wake    the disturbed water left astern of a boat.
  • Weather helm    a tendency of a boat to turn into wind.
  • Weather side    the side of the boat on which the wind is blowing.
  • Whisker pole    a light pole used to hold out the clew of a headsail when running
  • Winch    a winch is a mechanical device consisting usually of a metal drum turned by a handle around which a line is wound to give the crew more
    purchasing power when hauling taut a line.
  • Windage    those parts of a boat which increase drag for example rigging, spars, crew etc.
  • Windlass    a winch with a horizontal shaft and a vertical handle used to haul up your anchor chain.
  • Windward    the direction from which the wind blows toward the wind (opposite to leeward)



  • Yawl   a two-masted boat with the mizzen stepped aft of the rudder stock / post.

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