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Having a fully erect penis while wearing sweat pants.
"Dude, I got early the other morn'n and went to hardee's for a biscuit only to look down and see that I was totally sport'n a stiff biffy. The cashier called the cops when she saw the head peak'n out."
by P.T. Rodriquez October 05, 2006

Words related to Stiff Biffy

hard on pants stiffy sweat