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A friend of the girl you are boning who's job it is to take care of your balls.

Usually less attractive than the girl you're fucking, but can still perform a vital function - like letting old people greet at walmart
Girl 1: "I'd love to go to your place, but I need to drop my friend home"
Guy: "No probs, she can join us and be my nut valet"
Girl 2: "It's better than nothing, let's go"

Guy 1: "My gals less attractive friend is staying over tonight"
Guy 2: "Nut valet?"
Guy 1: "Nut valet!"
by nipplenibble January 28, 2011