butt lift

English Wikipedia has an article on:

buttock augmentation

Wikipedia

• buttlift

From butt +‎ lift.

butt lift (plural butt lifts)

1. (informal, Canada, US) A type of cosmetic surgery to increase the size of one's buttocks.

   Synonyms: arse lift, ass lift

   • 1984, H. L. Stryker, Obsessed: two novels‎^[1]:

     Fixing onto your voice, I simultaneously, in my mind's eye, check to see how Babs is doing with the plastic surgery, her buttlift, and I know she's made no attempt at all to reduce, but instead steadfastly clings to her fat.