An undergarment that supports the buttocks. Also: buttbra.
In appearance, the Biniki is similar to the kind of complicated Victorian undergarments you read about in your Brontes class in college. Consisting of two leg loops and a waistband, this foundation garment encircles the buttocks and "lifts and smoothes" the back of the upper thigh (which, when you hit 30, may or may not look like a burlap bag full of doorknobs). This device is often referred to, subtly, as a "butt bra."
—Emma Downs,, "A thing of booty," Fort Wayne Journal-Gazette, March 2, 2006
Regarding Mark's disdain for Australia's alliance with the United States, the obvious point needs to be stressed. The US has given us The Simpsons, South Park, Hungry Jack's, David Letterman, McNuggets, Mr Ed, Starbucks, novelisations of film musicals, liposuction, Survivor, free internet porn, Paris Hilton, Anna Nicole Smith and butt bras. Lay off.
—Jim Schembri, "Setting the record straight on my mate Mark," The Age, September 23, 2005
BEVERLY SCHUCH: You do. Now you have something new coming out called the butt bra.
SERGIO OXMAN: Well, it's called really the bella bra technically, but it is an enhancing item that really gives an opportunity to the woman to enhance all the most beautiful parts.
—"Cosabella - Co-Owner," CNNfn, April 11, 2000