Escapement

n.	1.	The act of escaping; escape.
	2.	Way of escape; vent. An escapement for youthful high spirits. - G. Eliot.
	3.	The contrivance in a timepiece which connects the train of wheel work with the pendulum or balance, giving to the latter the impulse by which it is kept in vibration; - so called because it allows a tooth to escape from a pallet at each vibration.

Noun

1.

escapement - mechanical device that regulates movement

escape wheel, mechanical device, timekeeper, timepiece