I'm Doing Ur Mom - It's a messy joke that means you're getting some with your f

It's a messy joke that means you're getting some with your friend's mom and you're probably going to get grounded.

She said, 'I'm doing ur mom, and I'm doing it in the backyard.'

He texted, 'I'm doing ur mom, and I'm doing it in the middle of the day.'

He said, 'I'm doing ur mom, and I don't care if you tell your dad.'