cave in vs buckle

cave in and buckle both are nouns.

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

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

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

cave in (noun)	buckle (noun)
the sudden collapse of something into a hollow beneath it	fastener that fastens together two ends of a belt or strap; often has loose prong
	a shape distorted by twisting or folding

cave in (verb)	buckle (verb)
break down, literally or metaphorically	bend out of shape, as under pressure or from heat
	fasten with a buckle or buckles
	fold or collapse