(in fishes) either of a pair of fins usually situated behind the head, one on each side, and corresponding to the forelimbs of higher vertebrates.
Origin of pectoral fin
First recorded in 1760–70
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for pectoral fin
either of a pair of fins, situated just behind the head in 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