the but crack that is visible when one is either crouching or sitting resembling a plumber fixing a toilet. Usually causes one to be grossed out unless your into that kind of stuff.
Steve-"Dude I'm about to puke from looking at that girls plumber's crack"
Josh-"I know man it's disgusting!"
Steve+Josh-"Pull up your pants!"
See also Bum Crack and Plumber. In general, when you have a water leak and you call a plumber to check it out, they always show up, bend over and a portion of their crack can be seen above their beltline.
Ha ha. She bent over to give Carly a hug and she showed a plumber's crack.