Merriam-Webster's Collegiate® Dictionary, 11th Edition
FLAP
I. noun
Etymology: Middle English flappe
Date: 14th century
a stroke with something broad ; slap , something broad and flat used for striking, something that is broad, limber, or flat and usually thin and that hangs loose or projects freely: as, a piece on a garment that hangs free, a part of a book jacket that folds under the book's cover, a piece of tissue partly severed from its place of origin for use in surgical grafting, an extended part forming the closure (as of an envelope or carton), the motion of something broad and limber (as a sail or wing), a movable auxiliary airfoil usually attached to an airplane wing's trailing edge to increase lift or drag,
6. a state of excitement or agitation ; tizzy , uproar , something (as an incident or remark) that generates an uproar, a consonant (as the sound \\d\\ in ladder and \\t\\ in latter ) characterized by a single rapid contact of the tongue or lower lip against another point in the mouth,
II. verb (flapped; flapping)
Date: 14th century
transitive verb to beat with or as if with a flap, to toss sharply ; fling , to move or cause to move in flaps, intransitive verb to sway loosely usually with a noise of striking and especially when moved by wind,
2. to beat or pulsate wings or something suggesting wings, to progress by flapping, to flutter ineffectively, to talk foolishly and persistently