A very flexible term for a frat boy, a group of them, or their mental outlook on life. Derives from the cold hard fact that no one other than an asshole would buy or wear a grad ring. Therefore, by a clever trick of logic you can safely assume any frat boy you meet owns a grad ring.
Did you see the size of that guy's grad ring?! (accusatory)
John got drunk and went all grad ring on us.
When the grad rings arrived at the party, we knew it was time to jam out.