The word Flap can refer to several things.
- A flap (aircraft) is a hinged surface on the trailing edge of an airplane wing.
- Flap, in (archaic) computer science jargon, refers to the process for unmounting a magnetic tape. When the system operator commanded a tape drive to unmount a tape, it would rewind the medium and then, as the tape unwrapped from the take-up reel, it would go "flap-flap-flap" as the feed reel spun down.
- In plastic surgery, a flap is a vascularised tissue transfer .
- In phonetics and phonology, a flap consonant is a sound produced by brief contact between the tongue and the roof of the mouth.
- In the phonology of English, flapping is a process by which a /t/ phoneme before an unstressed vowel is pronounced as a flap consonant.
- Flapping can also refer to a repetitive up-and-down motion most commonly associated with a bird's wing in flight. Birds flap to provide airflow against their wing, thereby generating lift. Larger wings are more efficient (a side-effect of their aspect ratio) so smaller birds must flap much more quickly, while larger birds can soar without flapping for long periods.