An acronym that initially stood for game recognize game; however, the acronym has since assumed its own meaning. The acronym now means an ongoing positive situation, typically involving the opposite sex (or the same sex if you swing that way). GRG may also be used as a synonym for sexual intercourse.
You are at a club and notice a hot girl that keeps staring at you. You turn to your friend and say, "I've got a GRG situation"
You gave out your number to the girl above and are currently awaiting her call. You receive a call from your friend, who is interested to know whether she has called, he asks "any GRG today." You reply, "no" as she has not yet called.
The girl above finally calls and you arrange for a date. You don't return home until the next day. You are greeted at the door by your friend who asks, "Did you get any GRG?" You reply "No, but things got pretty spicy."