bum bra
n.— «I noticed the denim was pulling across the top of the back of my legs. Dang, I thought, too tight. Then the clerk pointed at the taut fabric and said, “That’s the bum bra.”… It’s a dynamic trio of jean design elements: the cut of the inseam, the length of the rise and the positioning of the pocket. Put them together and voila! Booty boost.» —“Bootie bra works wonders” by Elizabeth Withey The Province (Vancouver, Canada) Oct. 21, 2007. (source: Double-Tongued Dictionary)