Question

What is a synonym for collapse

Answer 1

Falls/closes in/caves in Ex: during the storm the walls were closing in badly and the house collapsed more synonyms are breaks down and falls apart

Answer 2

Depends on how the word is being used. 
(of a structure) cave in, fall in, subside, fall down, give (way), crumple, buckle, sag, slump(of a person)faint, pass out, black out, lose consciousness, keel over, swoon; informal conk out
(of an institution or undertaking) break down, fail, fall through, fold, founder, miscarry, come to grief, be unsuccessful;