When a handjob is so constricting that the white's of the person performing the jobs knuckles are visible.

A women or girl who upon giving one a hand job, grabs and holds on for dear life. They grasp until their knuckles turn a faint tan or white color. In some extreme conditions, friction burns may result.

Term that refers to the male hand while induldging in the act of self-pleasure. Such as masturbation.

when a chick is jerking you off and you shoot a load all over her knuckles

When Victor grabs his penis and squeezes too tight, thus, causing his knuckles to turn white.

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).