This list of ship directions explains dozens of related terms such as fore, aft, astern, aboard, or topside. For background, see below: Origins.
abaft (preposition): at or toward the stern of a ship, or further back from a location, e.g. the mizzenmast is abaft the mainmast.
aboard: onto or within a ship, or in a group.
above: a higher deck of the ship.
aft (adjective): toward the stern of a ship.
adrift: floating in the water without propulsion.
aground: resting on the shore or wedged against the sea floor.
ahull: with sails furled and helm lashed alee.
alee: on or toward the lee (the downwind side).
aloft: the stacks, masts, rigging, or other area above the highest solid structure.
amidships: near the middle part of a ship.
aport: toward the port side of a ship (opposite of "astarboard").
ashore: on or towards the shore or land.
astarboard: toward the starboard side of a ship (opposite of "aport").
astern (adjective): toward the rear of a ship (opposite of "forward").
athwartships: toward the sides of a ship.
aweather: toward the weather or windward side of a ship.
aweigh: just clear of the sea floor, as with an anchor.
below: a lower deck of the ship.
belowdecks: inside or into a ship, or down to a lower deck.
bilge: the underwater part of a ship between the flat of the bottom and the vertical topsides
bottom: the lowest part of the ship's hull.
bow (or stem): front of a ship (opposite of "stern")
centerline: an imaginary, central line drawn from the bow to the stern.
fore or forward: at or toward the front of a ship or further ahead of a location (opposite of "aft")
inboard: attached inside the ship.
keel: the bottom structure of a ship's hull.
leeward: side or direction away from the wind (opposite of "windward").
on deck: to an outside or muster deck (as "all hands on deck").
on board: somewhere on or in the ship.
outboard: attached outside the ship.
port: the left side of the ship, facing forward (opposite of "starboard").
starboard: the right side of the ship, when facing forward (opposite of "port").
stern: the rear of a ship (opposite of "bow").
topside: on the ship's main weather deck.
underdeck: a lower deck of a ship.
yardarm: an end of a yard spar below a sail.
waterline: where the water surface meets the ship's hull.
weather: side or direction from which wind blows (same as "windward").
windward: side or direction from which wind blows (opposite of "leeward").
First use of "aboard": 14th century
First use of "aft": 1580
First use of "outboard": 1694
First use of "inboard": 1830
First use of "belowdecks": 1897.
The word "ahoy" is not a direction, but rather an interjection used to hail a person or ship, or to attract attention. See the linked sources, below, for more details.
