callipygian (kal-uh-PIJ-ee-uhn) adjective:
[From Greek calli- (beautiful) + pyge (buttocks).]
Having well-shaped buttocks.
[At right, the Aphrodite Kallipygos (Venus of the beautiful buttocks) lifting her robe and gazing down at her assets.]
"And it hasn't been lost on modern film directors that a nice set of tights can showcase the callipygian assets of a well-formed leading man."
-- Heroes in Hosiery; South China Morning Post (Hong Kong); Jul 20, 2006.
also brings to mind the delightful word steatopygia (noun) --
[from the Greek steat (fat) + pyge (buttocks)]
an excessive accumulation of fat on the buttocks (adj. steatopygic or steatopygous)