bust up v.
1. [late 19C+] (also bust) to have a major quarrel, to end a love-affair, to divorce.
2. [20C+] to stop something, e.g. a fight, happening.
3. [1920s+] to conclude, e.g. an evening out or a party.
4. [1980s+] (US) to make someone else laugh.
5. see bust v.1