Definition of thrashes:
(v) :
To beat mercilessly.
(v) :
To defeat utterly.
(v) :
To move about wildly or violently; to flail; to labour.
(n) :
(countable) A beat or blow; the sound of beating.
(v) :
To thresh.
(v) :
(software) To extensively test a software system, giving a program various inputs and observing the behavior and outputs that result.