The acronym for "gay butt sex orgy". It is one of many terms used to describe sexual interactions, such as lso, "lesbian sex orgy", mbso, "mixed butt sex orgy", and kgbso, "russian butt sex orgy". There is a tumblr page dedicated to the subject: gbso.tumblr.com
Will: Hey Dave, want to have a gbso tonight?
Dave: Man how 'bout an mbso?
Will: I guess you're wanting some variety after only men for a few weeks.
Dave: Yeah, how about some Russians too?
Will: Ok I'll ask Ivan to make the kgbso.
Dave: Man how 'bout an mbso?
Will: I guess you're wanting some variety after only men for a few weeks.
Dave: Yeah, how about some Russians too?
Will: Ok I'll ask Ivan to make the kgbso.
by Dicktionary123 February 2, 2015