falling out vs rupture

falling out and rupture both are nouns.

Word	Noun	Adjective	Verb	Adverb
falling out	Yes	No	No	No
rupture	Yes	No	Yes	No

As nouns, falling out and rupture are synonyms defined as:

falling out and rupture: a personal or social separation (as between opposing factions)

Other synonyms of falling out include breach, break, rift, severance.

falling out (noun)	rupture (noun)
a personal or social separation (as between opposing factions)	the act of making a sudden noisy break
	a personal or social separation (as between opposing factions)
	state of being torn or burst open

falling out (verb)	rupture (verb)
	separate or cause to separate abruptly