Quick definitions from WordNet (thrash)

▸ noun:  a swimming kick used while treading water
▸ 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:  beat thoroughly in a competition or fight
▸ verb:  move or stir about violently ("The feverish patient thrashed around in his bed")
▸ verb:  dance the slam dance
▸ name:  A surname (rare: 1 in 33333 families; popularity rank in the U.S.: #4277)

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▸ Also see thrash