fin

B1 · Intermediate Countable noun Sports

n. a long, flat rubber shoe that you wear to swim faster underwater.

n. a flipper-like device worn on the feet to increase propulsion while swimming or diving.

“You should wear fins and a mask if you want to go snorkeling.”

“The diver kicked his fins powerfully to reach the coral reef before the current shifted.”

B2 · Upper Intermediate Countable noun Technology Technical

n. a flat part on a plane, rocket, or machine that helps it stay steady or cool down.

n. a fixed or adjustable vane used for aerodynamic stability or to increase the surface area for heat dissipation.

“The small fins on the back of the rocket help it fly straight.”

“The engine's cooling fins were clogged with dust, causing the internal temperature to rise dangerously during the long flight.”

C1 · Advanced Countable noun Slang · British English · American English

n. a slang word for a five-pound note or five dollars.

n. a slang term for a five-unit currency note, specifically five pounds in the UK or five dollars in the US.

“He handed the shopkeeper a fin to pay for the magazine.”

“In the old detective novel, the protagonist slipped the informant a fin in exchange for the address of the warehouse.”

C1 · Advanced Technical

v. to cut the fins off a fish, especially a shark.

v. to remove the fins from a fish, often used in the context of the controversial practice of shark finning.

“Many countries have banned the practice of finning sharks at sea.”

“The environmental agency reported that thousands of sharks are illegally finned every year to satisfy the demand for specialty soups.”