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 6, 2006
Get the Stiff Biffy mug.