Acronym meaning "Official Blow Off". Defined as the formal notification given to someone when they are truly not interested and the fade away has finally kicked in.
After numerous phonecalls that Jen made to Rick were unanswered, she finally realized that she had been given the OBO.
"Wow she's totally obo," Carley commented to her friend of a chunky girl in the ice cream parlor, scarfing down a giant sundae like she'd never seen food.