(n.) 1. A mechanical device that extends and retracts the door bolt(s)of a safe, normally engaged by closing the door and disengaged by a time lock.
(n.) 2. A mechanical device (usually electrically powered) that extends and retracts the bolt of a safe lock. It is commonly disengaged by an electronic input such as that from a keypad.

Source: Lock Industry Standards and Training (LIST) Council