The antithesis of a cock block; a gameblock occurs when one's girlfriend/wife/partner somehow prohibits him or her from playing video games with his or her friends. This commonly occurs when the girlfriend is out of town or in a long distance relationship and a phone call prevents or interrupts game play.
Jay: Hey Percy, thanks for inviting all 31 of us over for this amazing Smash Brothers Tournament.
Percival: Yea man, it is going to be a great time---(Phone Rings)----Hang on guys its my girlfriend, I'll be right back
(1 hour later)
Percival: Where did everyone go? Damn it, I just got gameblocked pretty hard core.