Noah Webster's New International Dictionary of the English Language
1. (v.) Anything broad and limber that hangs loose, or that is attached by one side or end and is easily moved; as, the flap of a garment.
2. (n.) A hinged leaf, as of a table or shutter.
3. (n.) The motion of anything broad and loose, or a stroke or sound made with it; as, the flap of a sail or of a wing.
4. (n.) A disease in the lips of horses.
5. (n.) To beat with a flap; to strike.
6. (n.) To move, as something broad and flaplike; as, to flap the wings; to let fall, as the brim of a hat.
7. (v. i.) To move as do wings, or as something broad or loose; to fly with wings beating the air.
8. (v. i.) To fall and hang like a flap, as the brim of a hat, or other broad thing.