What is Rear Cleavage?
1.
Another way of referring to someone's ass crack that's hanging out. Hence the "rear" in the term.
Same as saying "
*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."
See