Originating from re-wording the lyrics to Soulja Boy's Pretty Boy Swag, frat boy swag is simply having an ere about you that screams "I'm awesome because I'm in a frat." A boy in kacki shorts, a polo, topsiders and occasionally a backwards baseball cap has major frat boy swag. Bonus points to those who are good looking, AND have frat boy swag.
Me-"Hey Jeff! You're looking pretty fratastic tonight!"
Jeff-"Fratastic? This right here my frat boy swaggg!"