To beat out grain from, as straw or husks; to beat the straw or husk of (grain) with a flail; to beat off, as the kernels of grain; as, to thrash wheat, rye, or oats; to thrash over the old straw.(verb)
source: webster1913
To practice thrashing grain or the like; to perform the business of beating grain from straw; as, a man who thrashes well.(verb)