A phrase used by chavs meaning i had sex with ya mam or just trying to bring your mam into the conversation. Many chavs use this as they think everyone gets offended when you mention their mam. Its funny the first time but after that when people start saying it to every little thing it gets boring.
Chav: ya mam
me: what about her?
Chav: i shagged her last night
Me: i know you did, she said you were shit.