break up vs split up

break up is not a noun while split up is a noun.

Word	Noun	Adjective	Verb	Adverb
break up	No	No	Yes	No
split up	Yes	No	Yes	No

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

Other hypernyms of break up include break, come apart, fall apart, separate.

As verbs, break up and split up are synonyms defined as:

break up and split up: discontinue an association or relation; go different ways

Other synonyms of break up include break, part, separate, split.

As verbs, split up is a hyponym of break up; that is, split up is a word with a more specific, narrower meaning than break up:

break up (noun)	split up (noun)
	an increase in the number of outstanding shares of a corporation without changing the shareholders' equity

break up (verb)	split up (verb)
laugh unrestrainedly	become separated into pieces or fragments
break or cause to break into pieces	get a divorce; formally terminate a marriage
come to an end	discontinue an association or relation; go different ways
separate (substances) into constituent elements or parts	separate into parts or portions
cause to go into a solution
cause to separate
close at the end of a session
bring the association of to an end or cause to break up
make a break in
set or keep apart
break violently or noisily; smash
attack with or as if with a pickaxe of ice or rocky ground, for example
release ice
destroy the completeness of a set of related items
take apart into its constituent pieces
suffer a nervous breakdown
disband
to cause to separate and go in different directions
discontinue an association or relation; go different ways