PEE-GRET
the feeling that you made a terrible mistake by not taking a leak at the office or home or wooded lot that you just left because you are, or know you soon will be, DYING to take a piss and you don't have an acceptable place to do it.
I am experiencing deep PEE-GRET right now; i should have taken a leak at that bar we just left...now i'm stuck in this car in downtown traffic and i'm DYING to go!