the world > life > the body > structural parts > muscle > [verb (intransitive)] > muscular movement (4)
intransitive. To contract the muscles of the body, usually involuntarily; to shrink into a bent or crooked position; to cower. Also (of a part of the…
(un-, prefix2 affix 1a affix 1b(b).)
intransitive. Of muscle: to undergo fibrillation (sense 1b).
intransitive. To bend or be capable of bending. Of a muscle: to contract. Also, = to flex one's muscles. Originally U.S.