Flap \Flap\, v. t. [imp. & p. p. {Flapped}; p. pr. & vb. n. {Flapping}.] [Prob. of imitative origin; cf. D. flappen, E. flap, n., flop, flippant, fillip.] 1. To beat with a flap; to strike. Yet let me flap this bug with gilded wings. --Pope. 2. To move, as something broad and flaplike; as, to flap the wings; to let fall, as the brim of a hat. {To flap in the mouth}, to taunt. [Obs.] --W. Cartwright.