Escapement

Webster's Dictionary of the English Language

·noun Way of escape; vent.

II. Escapement ·noun The act of escaping; escape.

III. Escapement ·noun 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.