Abbreviation for "Go suck your own cock!" An exclamation of exasperation, usually uttered when you want to finish a never ending argument. Inviting your nemesis to perform fellatio on himself, which for 99% of males is physically impossible, is a sure way to A) close a conversation, B) add to your nemesis' anger, and C) confuse him, esp. if you are both male, both straight and never demanded that you suck him off in the first place.
Mike: How about that G8 summit, they say they are going to reduce greenhouse gas emissions by 2020...
Bill: those bloody politicians! they personally create more greenhouse gases then a city block full of apartment buildings, what with their big cars, their private jets and so on...
A term of endearment for your homies and cronies. What up gsmack? Nuthin much Jeeves! We be just gsmackin around the way in our ridez yo. It can also be a verb and a state of being. Just gsmack back a little and chillz da fruck out.
Me and my gsmack are rollin and coast locin', listenin to some beats.