G/G/B stands for Girls/Girls/Boys, off of Panic! at the Disco's album, Too Weird To Live, Too Rare to Die. In the music video, Brendon Urie (the lead singer) is almost naked.
G.B.C.- Glorified booty call,is when someone is someone's steady fuck buddy,but really does not care, or love them as much as they act. Generally a semi- girlfriend,or semi-boyfriend who is fucking you just because they can,and maybe they like you just a little bit too.