A common euphemism a girl may use for the act of fingering herself. Similarly, "painting her nails red" can sometimes refer to a girl fingering said cooter whilst she is menstruating.
guy #1: "So what's Sally up to tonight? Is she gonna chill with us?"
guy #2: "She said she's just staying in and painting her nails tonight. How fuckin' boring is that."
guy #1: "This is like the 3rd time this week she's blown us off to paint her nails, how many times does one person need to paint their nails?"
Used to describe the 'job' of a woman who leaves all the breadwinning to her partner, so instead has 'occupation' of sitting home and enjoying the comfort of doing nothing. The term derives from what women apparently love doing best as their pastime.
"He goes out and works his butt off while she sits at home, painting her nails"
It is said of the situation where a person has the bad luck to make contact with his testicles against an undefined surface or object, intentioned or not.
Given the nature of the word, it is more appropriate to design cases where the interaction is made with a moving object, for example, a ball.
Although it is extremely painful for the victim, it tends to be considerably funny to people who witness it.
Today in the baseball game the pitcher took a nutshot; the baseball hit him in the nuts.
Man, I just watched the funniest nutshot video ever.