Thrash  —v. 1 beat or whip severely. 2 defeat thoroughly. 3 deliver repeated blows. 4 (foll. By about, around) move or fling (esp. The limbs) about violently. 5 = *thresh 1. —n. 1 act of thrashing. 2 slang (esp. Lavish) party.  thrash out discuss to a conclusion. [old english]