A fin like projection at the rear of a car, common on American cars of the 1950s. (noun)
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Use "tailfin" in a sentence
"In the fish markets of Asia, the tailfin from a basking shark can fetch nearly $10,000 (£5,250), a price tag justified not by its nutritional value, but its desirability as a vast sign on which restaurants can advertise their shark fin soup."
"The retro media centre was Thomas Thomassen's Final Major Project in BA (Hons) Modelmaking for Design and Media at the Arts Institute at Bournemouth -- it's an atompunk* tailfin fantasy that would look absolutely fantastic atop your giant console TV, serving as your home's media hub."
"Much of the detailing echoes Zeppelin design, while its V8 Ford engine is a mounted at the rear, under a long tailfin designed to both cool the engine and increase stability."