1.
If something such as a roof or a ceiling caves in , it collapses inwards.
Part of the roof has caved in...
= collapse
PHRASAL VERB : V P
2.
If you cave in , you suddenly stop arguing or resisting, especially when people put pressure on you to stop.
After a ruinous strike, the union caved in...
The Prime Minister has caved in to backbench pressure...
He’s caved in on capital punishment.
= give in
PHRASAL VERB : V P , V P to n , V P on n