What does the word flap mean?

Usage examples for flap

  1. The swans flew far too fast for the children to see where they were going, and when the swans began to flap more slowly so that the children could have seen if there had been anything to see, there was nothing to be seen, because it was quite dark. – Harding's luck by E. [Edith] Nesbit
  2. Swiftly, deftly, Jimmie Dale's hands rolled the rounded end of one of his collection of the legal instruments under the flap of the envelope, turned the sheets over and drew out the folded document inside. – The Adventures of Jimmie Dale by Frank L. Packard
  3. Lilly wiped her tears away with the flap of her riding gauntlet and smiled at him obediently. – The Song of Songs by Hermann Sudermann