"GG no re" Is an informalway to say "good game, no rematch". This word is often used in gaming. Saying this to someone is like saying that they are no match compared to you.
< You > Hey, Lets Have A Sword Fight In Insert Fighting Game
< Your Friend > Okay >:D
*Your Friend Loses The GameHorribly*
< You > GG no re
< Your Friend > D:
A popular Battle.net expression used to denote a substantial victory followed by no rematch. Often given before the fact in error. Literally: good game, no rematch, thanks