Rogets II: The New Thesaurus, Third Edition. 1995.
flail
VERB:
1. To beat (plants) with a machine or by hand to separate the grain from the straw: thrash, thresh. SeeATTACK, STRIKE. 2. To swing about or strike at wildly: thrash, thresh, toss. Idioms: toss and turn. SeeATTACK, MOVE, STRIKE.