cave in vs crumple

cave in is a noun but crumple is not a noun.

Word	Noun	Adjective	Verb	Adverb
cave in	Yes	No	Yes	No
crumple	No	No	Yes	No

As verbs, crumple is a hyponym of cave in; that is, crumple is a word with a more specific, narrower meaning than cave in:

Other hyponyms of cave in include go off, implode, buckle, flop, break, sink, slide down, slump.

cave in (noun)	crumple (noun)
the sudden collapse of something into a hollow beneath it

cave in (verb)	crumple (verb)
break down, literally or metaphorically	become wrinkled or crumpled or creased
	to gather something into small wrinkles or folds
	fold or collapse
	fall apart