Greater North American Perfect Ring-Out. In certain tournament video games, it refers to a tactic by which one player completely avoids being hit by their opponent, and also knocks them completely out of the ring. Compare to the LNA- the Lesser North American Perfect Ring-out, in which the above happens, but the winning player takes damage which is subsequently healed before the finishing maneuver.
That guy kept talking about how good he was, but I wound up getting a GNA on him.
If you keep up the trash-talk, I'll perform a GNA on you.