Definitions by Ray Boston

sack in the back 

The act of a male tucking his penis and balls between his legs (in a Buffalo Bill type style) while turning around, bending over and exposing his ass with bulging sack to passersby.

As my roommate Jim returned from the shower, he tried to gross me out by performing his "sack in the back" routine in my presence.

sack in the back by Ray Boston January 19, 2007