lock

A device operated by a key, combination, or keycard and used, as on a door, for holding, closing, or securing.

A section of a waterway, such as a canal, closed off with gates, in which vessels in transit are raised or lowered by raising or lowering the water level of that section.

A mechanism in a firearm for exploding the charge.

An interlocking or entanglement of elements or parts.

A hold in wrestling or self-defense that is secured on a part of an opponent’s body.

A secure hold; control.

A sure thing; a certainty.

To fasten the lock of.