Extensor

·noun A muscle which serves to extend or straighten any part of the body, as an arm or a finger;

— opposed to flexor.

extensor
extensor, ōris, m. [extendo], he who stretches (i. e. upon the rack), a torturer , Ambros. de Ja...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.