(1):
(n.) Something serving to rouse or excite.
(2):
(v. t.) To strike with the nail of the finger, first placed against the ball of the thumb, and forced from that position with a sudden spring; to snap with the finger.
(3):
(v. t.) To snap; to project quickly.
(4):
(n.) A jerk of the finger forced suddenly from the thumb; a smart blow.