This is an acronym that stands for:
Fuck you, bitch!
Except instead of a Y for you, its a U because its pronounced either fun, or
F U, B.
Origin:
middle of junior high study hall.
Lana: Mr. G, whenever I tell donovon hes off dress code he says, F U, B!
Tony:
hey, that spells FUB!
Jen: Hehe, I like it.
*later*
Mr. G: Cameron and Nathan, you are being to loud.
Jen: (to Nathan and Cameron) Oh, FUB!!!
Tony: wow, that was amazing.
Bianca: Haha, nice.
Meagan: would it be fubs, or FUB for the plural?
Jen: just FUB