"butt + cleavage= Bleavage"
1. Any showing of the butt when it is intended to be covered up by clothing.
2. When shorts are so short that a person's butt hangs out of the bottom.
3. When a person bends down and their butt crack is exposed.
"omg, did you see becky's shorts in gym class? she's totally got some bleavage going on"
A contraction of "back cleavage." Often occurs when a fat woman wears a tight bra, tank top or other garment that shows off the back area, thus squishing the back fat together to give the illusion of cleavage on their back.
That tank top is giving that girl some serious bleavage.