"Playing the dozens" refers to the act of participating in a popular insult-themed street game called The Dozens. The game is also known as Snaps in some areas.
When playing the dozens, participants practice keeping composure and quick-thinking skills. The game requires an audience, who act as a sort of panel of judges by voicing their approval of especially witty or low-down insults. The game usually features "Yo Momma" jokes and other insults about members of the opposing players' family and other sensitive issues. The dozens is often played in spoken word, but is also played by rhyming or rapping the insults.