cave

1 cave /ˈkeɪv/ noun
plural caves
1 cave
/ˈkeɪv/
noun
plural caves
Britannica Dictionary definition of CAVE
[count]
: a large hole that was formed by natural processes in the side of a cliff or hill or under the ground
2 cave /ˈkeɪv/ verb
caves; caved; caving
2 cave
/ˈkeɪv/
verb
caves; caved; caving
Britannica Dictionary definition of CAVE

cave in

[phrasal verb]
1 
a  : to fall down or inward
b  cave (something) in or cave in (something) : to cause (something) to fall down or inward
2 
informal : to stop trying to resist or oppose something : to give in or submit to pressure
— sometimes used in U.S. English without in — see also cave-in