This is what happens to adolescent boys when they sit around doing nothing.
A cockstand is an erection that happens throughout puberty due to the large amounts of androgens floating around the teenager's body. A cockstand can only be remedied by masturbation.
During English class, Missy notices Stephen has what it seems like a hard object sticking up on the frontal section of his pants. Fraught with curiosity Missy asks:
Missy: What's that sticking up on Stephen's pants?
Derrick: He's got a cockstand Missy. (The whole class laughs).
2. Can also be used as an insult against person of choice.
A man ejaculates all over his cock and then presses it against his partner's skin (or clothing), leaving an imprint in cum that is the shape of his cock. His partner can then let the cockstain dry thoroughly for for a more lasting effect.
When you're banging a tranny in the butt when she is lying down. You're so into it that you don't see her jacking one off and she nuts on your Dick causing Cock Stained Balls.
Last night I was doing slippery Sally hard in the ass, right? All of a sudden she busts a nut right on my balls. Fuckin' cock stained balls, man...