From WordNet (r) 3.0 (2006):
thresh
v 1: move or stir about violently; "The feverish patient
thrashed around in his bed" [syn: convulse, thresh,
thresh about, thrash, thrash about, slash, toss,
jactitate]
2: move like a flail; thresh about; "Her arms were flailing"
[syn: flail, thresh]
3: beat the seeds out of a grain [syn: thrash, thresh]
4: give a thrashing to; beat hard [syn: thrash, thresh,
lam, flail]