break up v.
1. [late 19C–1930s] (US) to make someone very upset, to make someone ill with tension, to cause someone to cry.
2. [late 19C+] (orig. US, also break it up) to cause someone to laugh or applaud heartily; to applaud heartily.
3. [20C+] (US) to act hysterically, to act irrationally.
4. [1920s+] (also break) to collapse in laughter.