1) A group of jokes meant to criticize one's mother by saying that she is fat, ugly, stupid, etc.
2) A lame phrase someone I know keeps saying whenever I ask him a question about PE because he has it before me.
1) Yo mama so ugly people watch her during horror movies.
2) Me: Hey, what are we doing in Pe today?
Him: Yo Mama!
Me: Shut the f up.