1. a thin flat part that sticks out from the body of a fish or other sea animal, used for swimming and steering
2. a thin flat part on an aircraft, rocket, or other vehicle that provides stability
3. a thin projecting part on a radiator or heat sink that increases surface area for cooling
Usage: technical

Examples

• The shark’s dorsal fin cut through the water.
• Fish use their fins to swim and change direction.
• The rocket’s fins helped stabilize its flight path.
• The airplane’s tail fin was damaged in the storm.
• The radiator fins help dissipate heat from the engine.
• Dolphins have powerful fins for fast swimming.