Another way of referring to someone's ass crack that's hanging out. Hence the "rear" in the term.

Same as saying "butt cleavage."
*guy walks by with his ass crack showing due to his pants being down too low*

Person 1: "Whoa, that guy's got some major rear cleavage there!"

Person 2: "I know. That's kinda... gross."
by Kikyo Maaka May 30, 2009
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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.
by QuacksO April 9, 2015
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