escapement

noun

1. 1.The contrivance in a timepiece (winding wristwatch) 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.
2. 2.A mechanism found in devices such as a typewriter or printer which controls lateral motion of the carriage.
3. 3.An escape or means of escape.
4. 4.The number of fish that escape commercial fishing operations and travel upstream to spawn.