crack up vs sustain

crack up and sustain both are verbs.

Word	Noun	Adjective	Verb	Adverb
crack up	No	No	Yes	No
sustain	No	No	Yes	No

As verbs, sustain is a hypernym of crack up; that is, sustain is a word with a broader meaning than crack up:

Other hypernyms of crack up include get, have, suffer.

crack up (verb)	sustain (verb)
laugh unrestrainedly	undergo (as of injuries and illnesses)
rhapsodize about	establish or strengthen as with new evidence or facts
suffer a nervous breakdown	admit as valid
	supply with necessities and support
	provide with nourishment
	be the physical support of; carry the weight of
	lengthen or extend in duration or space