noun

1. anything flat and broad that is attached at one end and hangs loose or covers an opening the flap of a pocket
2. the motion or slapping sound of a swinging flap the flap of an awning
3. Archaic a blow with something broad and flat; slap
4. either of the two parts of a book's dust jacket that fold inside the book's covers and that usually contain a summary of the book's contents and a brief biographical sketch of its author
5. Informal a state of excitement, controversy, or agitation
6. Aeron. a pilot-controlled airfoil; esp., a section hinged to the trailing edge of a wing between the aileron and the fuselage, usually used to increase lift or drag
7. Phonet. a sound articulated with a single rapid touch of the tongue against the roof of the mouth
8. Surgery a piece of tissue partly detached from the surrounding tissue, as for grafting

Etymology: ME flappe < the v.

transitive verb flapped, flapping flap′·ping

1. to strike with something flat and broad; slap
2. to move back and forth or up and down as in beating the air, usually with some noise a bird flapping its wings
3. to throw, fling, slam, etc. abruptly or noisily

Etymology: ME flappen: prob. echoic

intransitive verb

1. to move back and forth or up and down, as in the wind; flutter
2. to fly or try to fly by flapping the wings
3. to hang down as a flap
4. Chiefly Brit., Slang to become excited or confused