Abandon ship! – An imperative to leave the vessel immediately, usually in the face of some imminent danger.                                      
Able Seaman -  More experienced crew member than an Ordinary Seaman or Landman                                          
Aboard – On or in a vessel.
Adrift – Afloat and unattached in any way to the shore or seabed, but not under way.
Aft (Abaft)  – Towards the stern (of the vessel).
Afloat – Of a vessel which is floating freely (not aground or sunk). More generally of vessels in service ("the company has 10 ships afloat").
Aground – Resting on or touching the ground or bottom.
Ahoy – A cry to draw attention. Term used to hail a boat or a ship, as "Boat ahoy!"
All hands – Entire ship's company, both officers and enlisted personnel.
Aloft – In the rigging of a sailing ship. Above the ship's uppermost solid structure; overhead or high above.
Anchorage – A suitable place for a ship to anchor either off a port or the coast.
Ashore – On the beach, shore or land.
Astern – Behind the stern (back) of the ship. An object or vessel that is abaft another vessel or object.
Avast – Stop! Cease or desist from whatever is being done.
Awash – So low in the water that the water is constantly washing across the deck.
Aye, aye – Reply to an order or command to indicate that it, firstly, is heard; and, secondly, is understood and will be carried out. ("Aye, aye, sir" to officers).

Bear away – Turn away from the wind or from a port or another vessel.
Bear down - Turn or move towards other vessels or the land.
Bearing – The horizontal direction of a line of sight between two objects on the surface of the earth.
Belay - Stop or make fast.
Bilge – The bilge is the compartment at the bottom of the hull of a ship or boat where water collects so that it may be pumped out of the vessel at a later time.
Binnacle – The stand on which the ship's compass is mounted. 
Bosun (Boatswain) - Officer in charge of ship's crew and equipment.                                                                                     
Bow – The front of a ship.
Bowline - Rope attached to the side of a sail.
Bring to (Bring up) – Cause a ship to be stationary by arranging the sails.
Broach – When a vessel loses control and is forced beam on (sideways) to the sea and swell, possibly causing her to capsize.

Capstan - Rotating cylinder used to wind in cables, such as the anchor cable.
Chafing – Wear on line or sail caused by constant rubbing against another surface.
Chock-a-block – Rigging blocks that are so tight against one another that they cannot be further tightened.                                    
Cox (Coxswain) - Person in charge, particularly, of the ship's steering
(As the) crow flies – A direct line between two points (which might cross land) which is the way crows travel rather than ships which must go around land.                                                                                                                                                                
Crow's nest – A structure with sides and sometimes a cover, constructed around a mast near to the top, for lookouts.

Davy Jones' Locker – A seafarer's expression for the bottom of the sea.
Deck hand – A person whose job involves aiding the deck supervisor in (un)mooring, anchoring, maintenance, and general evolutions on deck.

Fathom – A unit of length equal to 6 feet (1.8 m), roughly measured as the distance between a man's outstretched hands. Particularly used to measure depth.
Figurehead – Symbolic image at the bow of a ship.
First Mate – The second in command of a ship.
Flotsam – Debris or cargo that remains afloat after a shipwreck.
Footrope – Each yard on a square rigged sailing ship is equipped with a footrope for sailors to stand on while setting or stowing the sails                                                                                                                                                                                                                                                                                                                                                                                                         Forecastle (fo'c'sle) - Traditionally the sailors' living quarters in the fore part of the vessel.
Forecastle head (fo'c'sle head) - The deck above the fo'c'sle.
Furl – To roll or gather a sail against its mast or spar.

Galley – The kitchen of the ship.
Gangway – The means of boarding or leaving a vessel. Applies to the opening in the bulwark of the ship and the method of passing from shore to ship or vice versa.
Ghost – To sail slowly when there is apparently no wind.
Going about or tacking – Changing direction at sea for sailing ships.
Gooseneck – Fitting that attaches the boom to the mast, allowing it to move freely.
Grog – Watered-down "pusser's rum" consisting of half a gill with equal part of water, issued to all seamen over twenty.
Groggy – Drunk from having consumed a lot of grog.

Heads - Toilets.
Heave – The act of hauling or heaving. Also a vessel's transient, vertical, up-and-down motion.
Helmsman – A person who steers a ship

Jetsam - Cargo or wreckage thrown overboard to lighten the ship (as opposed to floating off).
Jib – A triangular staysail at the front of a ship.
Jury - Makeshift.

Keel – The central structural basis of the hull
Knot – A unit of speed: 1 nautical mile (1.1508 mi) per hour. Originally speed was measured by paying out a line from the stern of a moving boat.
Know the ropes – A sailor who 'knows the ropes' is familiar with the miles of cordage and ropes involved in running a ship.

Ladder – On board a ship, all "stairs" are called ladders, except for literal staircases aboard passenger ships.
Landlubber – A person unfamiliar with being on the sea.
Lanyard – A small line used for securing objects.
Lay – To come and go, used in giving orders to the crew, such as "lay forward" or "lay aloft".                                                
Leadsman - Crew member responsible for heaving the lead line to take soundings of the depth of water below the ship.
League – A unit of length, normally equal to three nautical miles.
Line – The correct nautical term for the majority of the cordage or "ropes" used on a vessel.
List – The vessel's angle of lean or tilt to one side.
Loaded to the gunwales – Literally, having cargo loaded as high as the ship's rail; also means extremely drunk.

Making way – When a vessel is moving under its own power.
Mainmast (Main) – The tallest mast on a ship.
Man of war (Man o' war) – A warship from the Age of Sail
Man overboard! – A cry let out when a seaman has gone overboard.
Mast – A vertical pole on a ship which supports sails or rigging.

Navigation rules – The Regulations for the Prevention of Collisions at Sea.
No room to swing a cat – The entire ship's company was expected to witness floggings, assembled on deck. If it was very crowded, the bosun might not have room to swing the 'cat o' nine tails' (the whip).

Oakum – Material used for caulking hulls. Often hemp picked from old untwisted ropes and tarred.
Oilskins  – Foul-weather clothing worn by sailors.
Outward bound – To leave the safety of port, heading for the open ocean.

Pitch – A vessel's motion, rotating about the beam/transverse axis, causing the fore and aft ends to rise and fall alternately.
Poop (deck) – The uppermost after deck of a ship.
Port (Larboard) – Towards the left-hand side of the ship facing forward.
Porthole – An opening in a ship's side, esp. a round one for admitting light and air; the port being the fitting that covers it
Press gang – Formed body of personnel from a ship of the Royal Navy that would identify and force (press) men, usually merchant sailors, into service on naval ships; usually against their will.
Privateer – A privately-owned ship authorised by a national power to conduct hostilities against an enemy. Also called a private man of war.
Pusser (Purser) - The person who buys, stores and sells all stores on board ships, including victuals, rum and tobacco.

Quarterdeck - The deck forward of the Poop, from where the ship is controlled. Also the command post for battles at sea.
Quay/Quayside (Jetty or Pier) – The dock or platform to which vessels secure. 

Ready about – A call to indicate imminent change of direction.
Rigging – The system of ropes and lines used to control sails.
Roll – A vessel's motion from side to side.
Rope's end – A summary punishment device.

Seaman – Term for a low ranking sailor.
Seaworthy – Capable and fit for sea going.
Skipper – Slang term for the captain of a ship.
Spar - The "cross-piece" on the mast of a square-rigged ship which carries the sail.
Starboard – Towards the right-hand side of a vessel facing forward.
Stern – The rear part of a ship.

Under way – A vessel that is moving under control: that is neither at anchor, made fast to the shore, nor aground.

Waist – The central deck of a ship between the forecastle and the quarterdeck.
Watch – A period of time during which a part of the crew is on duty. Changes of watch are marked by strokes on the ship's bell.
Weigh anchor – To heave up (an anchor) preparatory to sailing.

Yard - A spar attached to the mast which carries the sail.
Yarr – Acknowledgement of an order, or agreement. Also "aye, aye".