(fin) noun
1. A membranous extension from the body of a fish or other aquatic animal, serving to propel, balance, or steer it in the water. For illustrations see FISH, RORQUAL.
2. Any finlike or projecting part, appendage, or attachment.
3. Naut. A finlike appendage to a submarine boat or the like; a fin keel.
4. Aeron. A fixed supplementary surface of an aircraft, usually vertical: a tail fin. See illustration under AIRPLANE.
5. A projecting rib on a radiator or on the cylinder of an internal–combustion engine.
6. Any finlike part, as on a rocket, bomb, etc.
7. A flipper (def. 2).
8. Mech. The projecting ridge of a metal casting at the line of junction with the mold.
—v. finned, fin·ning v.t. To cut up or trim off the fins of (a fish).
—v.i. To beat the water with the fins, as a whale when dying. [OE finn]

(fīn) v.t. & v.i. Scot.
To find.