dolphin

1. A carnivorous aquatic mammal in one of several families of order Cetacea, famed for its intelligence and occasional willingness to approach humans.
2. A fish, the mahi-mahi or dorado, Coryphaena hippurus, with a dorsal fin that runs the length of the body, also known for iridescent coloration.
3. A depiction of a fish, with a broad indented fin, usually embowed.
4. The dauphin, eldest son of the kings of France.
5. (history) A mass of iron or lead hung from the yardarm, in readiness to be dropped through the deck and the hull of an enemy's vessel to sink it.
6. A kind of wreath or strap of plaited cordage.
7. A spar or buoy held by an anchor and furnished with a ring to which ships may fasten their cables.
8. A mooring post on a wharf or beach.
9. A permanent fender around a heavy boat just below the gunwale.
10. One of the handles above the trunnions by which a gun was lifted.

noun

A man-made semi submerged maritime structure, usually installed to provide a fixed structure for temporary mooring, to prevent ships from drifting to shallow water or to serve as base for navigational aids.