Literally: Zero Bangs Until Proven Otherwise. This term is used to describe a girl who you naturally presume to be a virgin without having to inquire to heavily. However, it is not certain that she has zero bangs, so it could be proven otherwise. This type of girl is generally not ideal for pursuing/targeting, because you probably won't be able to bang her without a big time investment, unless you are freaking awesome. Once she has some bangs behind her, it is not such a grueling process, but bedding a girl who is ZBUPO can be exhausting.
"You're hitting on Sandy? Good luck, that could take a while."
"Why?"
"I don't know about Sandy for sure, but my direct assumption would be ZBUPO. She just seems so innocent."
"So between Sandy and her roommate, they have zero bangs?"
"Definitely zero bangs."
by Brickslayer121 October 31, 2011
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