split up is a verb and noun meaning "get a divorce; formally terminate a marriage". It carries 5 recorded senses.
discontinue an association or relation; go different ways
“The business partners broke over a tax question”
“The couple separated after 25 years of marriage”
“My friend and I split up”
become separated into pieces or fragments
“The figurine broke”
“The freshly baked loaf fell apart”
an increase in the number of outstanding shares of a corporation without changing the shareholders' equity
“they announced a two-for-one split of the common stock”
Definitions, synonyms and semantic relations for split up come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.