Definition of "Thrash" :

noun: a swimming kick used while treading water

verb: beat thoroughly and conclusively in a competition or fight

verb: give a thrashing to; beat hard

verb: beat the seeds out of a grain

verb: move data into and out of core rather than performing useful computation

"The system is thrashing again!."

verb: beat so fast that (the heart's) output starts dropping until (it) does not manage to pump out blood at all

verb: move or stir about violently

"The feverish patient thrashed around in his bed."

verb: dance the slam dance