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;