pucker factor number 9
A term that one uses to describe, and to discreetly convey in public, their urgency and need to visit a toilet to take a crap.  Number nine is always used as the guage to describe the tightness of the sphincter, which conveys that the person is right on the edge of crapping their pants.
"Hey man, I have to get out of here fast - I've got pucker factor number 9"