- the fin or finlike integumentary expansion generally developed on the back of aquatic vertebrates.
Origin of dorsal fin
First recorded in 1760–70
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for dorsal fin
In the figure there is represented the cross-section of a fish (its dorsal-fin D) just before the spear strikes.Along Alaska's Great River
- any unpaired median fin on the backs of fishes and some other aquatic vertebrates: maintains balance during locomotion
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012