Meaning of “cave in” - Learner’s Dictionary

cave in

phrasal verb with cave uk us /keɪv/ verb
FALL

If a ceiling, roof, or other structure caves in, it breaks and falls into the space below.

AGREE

to agree to something that you were against before, after someone has persuaded you or made you afraid:

The company has finally caved in to the demands of the unions.

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