Other forms: fins
A fin is the thin flap a fish steers and pushes with. Some for power, some for balance.
Different ones have names, so a dorsal fin stands on the back and a tail fin drives the fish forward. The dorsal fin breaking the surface is the standard image of a shark. Divers wear fins on their feet, called flippers in Britain. Aircraft and old cars have fins too, meaning any thin projecting surface, and 1950s American cars are remembered mainly for theirs.
1nounfinA thin flat part of a fish used for swimming and steering.
“A single fin cut through the water.”
2nounprojectingA thin projecting surface on a vehicle or aircraft.
“The old car had enormous tail fins.”
From fin, from finn, from finnō, finǭ (compare vin, Finne, fena), from *(s)pīn- (compare ind, pinna, xto.
Etymology from Wiktionary, CC BY-SA