Ass cleavage
From Voyeurweb's Wiki about Sex
Ass cleavage is a special form of cleavage and refers to the the enticing cleft located between her ass cheeks which is called ass crack. Ass cleavage can be made even more enticing when her ass cheeks are pushed together by clothing item like jeans.
Ass cleavage differs from Plumber's crack by degrees of attractiveness. A dude's jeans dropping low will result in Plumber's crack, each and every time it happens. A woman's low rise jeans will result in delicious ass cleavage, each and every time.

