Meaning of “hook” - Learner’s Dictionary

hook

noun uk us /hʊk/

B2 [ C ] a curved piece of metal or plastic used for hanging something on, or a similar object used for catching fish:

His coat was hanging from a hook on the door.
off the hook

If a telephone is off the hook, the part you speak into is not in its correct position, so the telephone will not ring.

a left/right hook

a hard hit with your left/right hand

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