A broad flat limb used for swimming, as those of seals, sea turtles, whales, etc.
- A wide flat limb, as of a seal, whale, or other aquatic mammal, adapted for swimming.
- A rubber covering for the foot having a flat flexible portion that widens as it extends forward from the toes, used in swimming and diving. Also called fin1.
- A flat lever in a pinball machine, used to hit the ball so it stays in play.