CubGG operates within the sweepstakes rules where they are legal. The Site does not permit members to wager real money and has no ability to accept deposits as it is a "free play" site only.
It's short for "good game," something poker players traditionally say when they bust from an online tournament, or to someone after they have busted, complimenting their play. It's also said sarcastically, pointing out someone's flawed play or unfortunate bust-out.