flap
     n 1: any broad thin and limber covering attached at one edge;
          hangs loose or projects freely; "he wrote on the flap of
          the envelope"
     2: an excited state of agitation; "he was in a dither"; "there
        was a terrible flap about the theft" [syn: {dither}, {pother},
         {fuss}, {tizzy}]
     3: the motion made by flapping up and down [syn: {flapping}, {flutter},
         {fluttering}]
     4: a movable piece of tissue partly connected to the body
     5: a movable airfoil that is part of an aircraft wing; used to
        increase lift or drag [syn: {flaps}]
     v 1: move in a wavy pattern or with a rising and falling motion;
          "The curtains undulated"; "the waves rolled towards the
          beach" [syn: {roll}, {undulate}, {wave}]
     2: move noisily; "flags flapped in the strong wind"
     3: move with a thrashing motion; "The bird flapped its wings";
        "The eagle beat its wings and soared high into the sky"
        [syn: {beat}]
     4: move with a flapping motion; "The bird's wings were
        flapping" [syn: {beat}]
     5: make a fuss; be agitated [syn: {dither}, {pother}]
     6: pronounce with a flap, of alveolar sounds
     [also: {flapping}, {flapped}]
Source: WordNet® 2.0

flap vt. 1. [obs.] To unload a DECtape (so it goes flap, flap,
   flap...). Old-time hackers at MIT tell of the days when the disk was
   device 0 and DEC microtapes were 1, 2,... and attempting to flap device
   0 would instead start a motor banging inside a cabinet near the disk. 2.
   By extension, to unload any magnetic tape. See also {macrotape}. Modern
   cartridge tapes no longer actually flap, but the usage has remained.
   (The term could well be re-applied to DEC's TK50 cartridge tape drive, a
   spectacularly misengineered contraption which makes a loud flapping
   sound, almost like an old reel-type lawnmower, in one of its many
   tape-eating failure modes.)


Source: The Jargon File