White Knuckler

When one has to shit so forcefully that it is required that one grips the top of the bathroom stall so tightly that your hands, and most notably your knuckles, turn white. Often accompanied by excessive groaning, tears,and, in truly tragic situations, blood. Happens when the body lacks water to a degree that your intestines are almost stopped up but can still be cleared with enough 'push'(not constipation, but just barely).