Fellatio, more commonly referred to as a blow job or oral sex being performed on a man.
"Hey Jane, Boss me up."
"Dude, Stacey gave me some great boss last night."
"I had a terrible day at work. I need a cold beer and some good boss."
"Did you see the way she was all over him? She definitely bossed him up in the car on the way home."
"Dude, did you get bossed up?
"Yup. It was Bosstastic!"
Stands for "kids a fuck up." This is a slang term teachers often use to refer to sub-intelligent or "stupid" kids whom the teacher realizes has little chance of success in the future.
"Did you see the list of kids I have in my class this year? They are all KAFUs."