Noun - An acronym that stands for massively Multiplayer Online Bulliten Board. Usually used to confront someone who takes an internet forum too seriously.
"Hehe, I have almost 44,000 posts, what are you going to do about that?"
"HOLY CRAP!!!!!!11 His quantity/quality nature causes me to be inferior to him! DAMN THIS MMOBB!!! DAMN YOU SPIDERMAN!!!"