belfie

Etymology
or.

Noun

 * 1)  A self-taken photograph of one's own buttocks.
 * 2) * 2015, Christmas Abbott (with Maggie Greenwood-Robinson), The Badass Body Diet: The Breakthrough Diet and Workout for a Tight Booty, Sexy Abs, and Lean Legs, HarperCollins (2015), ISBN 9780062390974, unnumbered page, published 12 May 2015:
 * Take several “before” pictures of your whole body and include a “belfie” (butt selfie) the day before you start the program. Do it from different angles — front, side, and back.
 * 1) * 2015, Christmas Abbott (with Maggie Greenwood-Robinson), The Badass Body Diet: The Breakthrough Diet and Workout for a Tight Booty, Sexy Abs, and Lean Legs, HarperCollins (2015), ISBN 9780062390974, unnumbered page, published 12 May 2015:
 * Take several “before” pictures of your whole body and include a “belfie” (butt selfie) the day before you start the program. Do it from different angles — front, side, and back.