[flail] n [ME fleil, flail, partly fr. (assumed) OE flegel (whence OE fligel), fr. LL flagellum flail, fr. L, whip & partly fr. MF flaiel, fr. LL flagellum--more at flagellate] (bef. 12c): a hand threshing implement consisting of a wooden handle at the end of which a stouter and shorter stick is so hung as to swing freely
[2]flail vt (15c) 1 a: to strike with or as if with a flail "arms ~ing the water" b: to move, swing, or beat as if wielding a flail "~ing a club to drive away the insects"
2: to thresh (grain) with a flail ~ vi: to move, swing, or beat like a flail