fin

1. One of the appendages of a fish, used to propel itself and to manoeuvre/maneuver. · The fish's fins minimize water flow.
2. A similar appendage of a cetacean or other marine animal. · a dolphin's fin
3. A thin, rigid component of an aircraft, extending from the fuselage and used to stabilise and steer the aircraft. · The fin stabilises the plane in flight.
4. A similar structure protruding from a projectile, used to help keep it on course.
5. A similar structure on the bottom of a surfboard, used to help steer it.
6. A hairstyle, resembling the fin of a fish, in which the hair is combed and set into a vertical ridge along the top of the head from about the crown to the forehead.
7. A device worn by divers and swimmers on their feet. · The divers wore fins to swim faster.
8. An extending part on a surface of a radiator, engine, heatsink, etc., used to facilitate cooling.

Plural fins