split up vs dissever

split up is a noun but dissever is not a noun.

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

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

Other synonyms of split up include carve up, divide, separate, split.

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

split up (verb)	dissever (verb)
become separated into pieces or fragments	separate into parts or portions
get a divorce; formally terminate a marriage
discontinue an association or relation; go different ways
separate into parts or portions