adj. Of, pertaining to, or having shapely buttocks.

Callipygæ and women largely composed behinde.
Pseudodoxia epidemica, Sir Thomas Brown (1646)

Because a shapely posterior deserves a word just as bootylicious.

While bar hopping with friends, do you worry about talking about a woman’s physical features without her hearing? Fear no more. “Bro, Check out that callipygian female!” Or you could use it as a noun… because I say you can. “Don’t look now. Callipygian: 9 o’clock!”

Ladies: Baby got back? Does your callipygous behind bring all the boys to the yard? If you ever hear “Damn girl! You is callipygian!” You know the man has a very large… vocabulary.