(in fishes) either of a pair of fins on the lower surface of the body, corresponding to the hind limbs of a land vertebrate; ventral fin.
Origin of pelvic fin
First recorded in 1905–10
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for pelvic fin
either of a pair of fins attached to the pelvic girdle of fishes that help to control the direction of movement 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