noun

• (aviation) A hinged surface on the trailing edge of the wings of an aeroplane, used to increase lift and drag.
• (phonetics) A consonant sound made by a single muscle contraction, such as the sound /ɾ/ in the standard American English pronunciation of body.
• (surgery) A piece of tissue incompletely detached from the body, as an intermediate stage of plastic surgery.
• (slang, vulgar, chiefly in the plural) The labia, the vulva.

verb

• (transitive) To move (something broad and loose) up and down.
  "The crow slowly flapped its wings."
• (intransitive) To move loosely back and forth.
  "The flag flapped in the breeze."
• (soccer, intransitive) For a goalkeeper to weakly attempt to play a flighted ball with the hands, failing to control it.
  "Former Turkey goalkeeper Rustu Recber flapped at his first Delap throw but was given a soft free-kick by referee Antony Gautier."
• (phonetics, transitive) To pronounce (something) as a flap consonant.