It does NOT mean Game Over, so stop trying to use it that way.
Above all else, just cause you died to First Blood, your Jungler took one last hit while you were dead, or a tower went down, doesn't mean you have to spam the chat with:
"Omg, this team, gg."
"OMFG ALWAYS ME GG, AFK."
"WOW WE LOOSE THIS NOOB TEAM, GEGE."
And all the other trash that follows along.
It's seriously negative, cause GG, often paired with WP is supposed to be a handshake after the game. "Nice job guys, you played well." It's NOT supposed to mean 'Game over, I'm afk, noob team'.