Thrashing rhymes with:
crashing, trashing, bashing, caching, cashing, clashing, crashing, dashing, fasching, flashing, gnashing, hashing, lashing, rehashing, slashing, smashing, splashing, stashing, trashing
Thrashing sounds like:
tarzan's, terrorizing, terseness, theorizing, thoroughness, torching, tracing, tracking, tragicomic, trajan's, trashing, tregoning, trekking, tricking, trojanowski, trojans, trucking, trzcinski