fin
One of the appendages of a fish, used to propel itself and to manoeuvre/maneuver.
Example
“The fish's fins minimize water flow.”
Other meanings
A similar appendage of a cetacean or other marine animal.
“a dolphin's fin”
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.”
Where this comes from
This definition is adapted from “fin” on Wiktionary, by its contributors, published under CC BY-SA 4.0. This page is published under the same licence.