dorsal fin

noun

plural dorsal fins

: a flat thin body part that projects from the back of many fish (such as trout, barracuda, and sharks) and some marine mammals (such as dolphins)

Porpoises have a more triangular dorsal fin while a dolphin's dorsal fin is more curved.

—Naomi Corrigan and Dave Himelfield

This member of the perch family has two dorsal fins and a large mouth outfitted with sharp teeth …

—Matt Markey

Examples of dorsal fin in a Sentence

Recent Examples on the Web

WeWhale said its team counted roughly 10 apparent pellet impacts on the left side of her dorsal fin. — Stepheny Price, FOXNews.com, 18 Aug. 2026

Spiny dogfish have two dorsal fins, each preceded by a sharp spine, according to NOAA. — Anthony Thompson, USA Today, 14 Aug. 2026

Guests at Brookfield Zoo can identify her in Dolphin Bay by her distinctive features, including a freckle on her tongue, pink coloration on her ventral side, and smaller flukes and dorsal fins in relation to her body size. — Adam Harrington, CBS News, 13 Aug. 2026

More high-quality footage that captures the orca’s dorsal fins and signature eye patches can help identify individuals. — Laura Baisas, Popular Science, 23 July 2026

Word History

First Known Use

1752, in the meaning defined above

Rhymes for dorsal fin

• aneurin
• crystallin
• eosin
• mandolin
• porphyrin
• superfine
• underpin
• vietminh
• violin
• akin
• auxin
• buckskin

Kids Definition

dorsal fin

noun

: a fin on the ridge along the middle of the back of a fish or sea mammal (as a whale)