dorsal fin

American  

noun

1. the fin or finlike integumentary expansion generally developed on the back of aquatic vertebrates.

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dorsal fin British  

noun

1. any unpaired median fin on the backs of fishes and some other aquatic vertebrates: maintains balance during locomotion

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Etymology

Origin of dorsal fin

First recorded in 1760–70

Example Sentences

"A dorsal fin slowly broke the surface revealing that familiar profile that looked like a shark," he said.

From BBC • May 16, 2025

Winter had put a life vest on the dog resembling a shark, with a dorsal fin protruding from its back.

From Los Angeles Times • Oct. 9, 2024

What they spotted, a whale without a dorsal fin, led the researchers to think that it might be a North Atlantic right whale, a critically endangered species that the aquarium has been closely monitoring.

From New York Times • Mar. 6, 2024

They can be identified by their lack of a dorsal fin and mottled appearance that makes them very different from whales more commonly seen off New England such as the humpback whale and minke whale.

From Seattle Times • Mar. 5, 2024

Based on the witnesses’ descriptions of size and the shape of the dorsal fin, area experts were trying to identify the type of shark.

From "The Line Tender" by Kate Allen