Thrash Thrash, Thresh Thresh, v. t. 1. To practice thrashing grain or the like; to perform the business of beating grain from straw; as, a man who thrashes well. 2. Hence, to labor; to toil; also, to move violently. I rather would be M[ae]vius, thrash for rhymes, Like his, the scorn and scandal of the times. --Dryden.