Rear-view cleavage
The groove between one's buttocks, sometimes visible if the person bends over too far, or if his/her pants/shorts are too short/loose. Unlike a buxom girl's chest-cleavage, a sumptuous-sized endowment "back there" is not an alluring feature, as a girl is considered **more** attractive/desirable if she has a **small** cute round rump.
Wistful stud: I sure wish I could find a bosomy gal with a nice firm little ass --- all of the chesty chicks I've befriended so far have had a rear-view cleavage that's at least as ample as their chest-meat.