splitsville vs breakup

splitsville and breakup both are nouns.

Word	Noun	Adjective	Verb	Adverb
splitsville	Yes	No	No	No
breakup	Yes	No	No	No

As nouns, breakup is a hypernym of splitsville; that is, breakup is a word with a broader meaning than splitsville:

splitsville: separation or breakup or divorce
breakup: the termination or disintegration of a relationship (between persons or nations)

Other hypernyms of splitsville include dissolution.

splitsville (noun)	breakup (noun)
separation or breakup or divorce	the termination or disintegration of a relationship (between persons or nations)
	coming apart