Merriam-Webster's Collegiate® Dictionary, 11th Edition
THRASH
I. verb
Etymology: alteration of thresh
Date: 1568
transitive verb to separate the seeds of from the husks and straw by beating ; thresh 1,
2. to beat soundly with or as if with a stick or whip ; flog , to defeat decisively or severely , to swing, beat, or strike in the manner of a rapidly moving flail ,
4. to go over again and again , to hammer out ; forge , intransitive verb thresh 1, to deal blows or strokes like one using a flail or whip, to move or stir about violently ; toss about , see: swing
II. noun
Date: 1840
an act of thrashing, rock music (as heavy metal or punk rock) that is extremely fast and loud