Abreviation for "You on your own".
Brent- Hey let's go watch netflix and chill. Don't forget the condoms.
Felicia- Nah, forget the condoms!
Brent- Why?
Felicia- YOLO!
Brent- Okay, and if you get pregnant, YOYO!
Felicia- What's that?
Brent- You On Your Own.