Usually used in a sentence involving yer friend banging her
Guess who I had sex with last night? Ya Mum!
awesome comeback for lowlifes who have no other decent insult to use
Fred: What's the time, man?
Jess: YA MUM!
Something you say when you see a British roadman
Roadman "Ayo where you from g"
Person "YA MUM"
Roadman "Ahhh i know where that is"