Meaning of “lock” - Learner’s Dictionary

lock

noun [ C ] uk us /lɒk/
IN DOOR

B1 the thing that is used to close a door, window, etc, and that needs a key to open it:

I heard someone turn a key in the lock.
safety locks
WATER

a place on a river with gates to allow boats to move to a different water level

(Definition of “lock noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)