Flinch

v. i.
  1. To withdraw from any suffering or undertaking, from pain or danger; to fail in doing or perserving; to show signs of yielding or of suffering; to shrink; to wince; as, one of the parties flinched from the combat.
  2. (Croquet) To let the foot slip from a ball, when attempting to give a tight croquet.

n.
  1. The act of flinching.