Girl's butt, that is rather large. Specifically relates to large butt cheeks and meaty area around the butthole. Interchangable term with donk. Usually used to describe a big butt in tight clothing or during a dance.
Often abbriviated as BHM in the conversations and guy-talk.

Adj. Something that is expected to have a long lifespan by virtue of having existed for a long time, based on the lindy effect, named for the New York restaurant Lindy's, coined by Albert Goldman and popularized by Nassim Taleb.