slide down vs cave in

slide down is not a noun while cave in is a noun.

Word	Noun	Adjective	Verb	Adverb
slide down	No	No	Yes	No
cave in	Yes	No	Yes	No

As verbs, cave in is a hypernym of slide down; that is, cave in is a word with a broader meaning than slide down:

Other hypernyms of slide down include break, collapse, fall in, founder, give, give way.

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

slide down (verb)	cave in (verb)
fall or sink heavily	break down, literally or metaphorically