Noun. Spent nuts are the male testicles after having been drained of all semen. They need a prolonged period to regenerate. Typically happens after an intense session of masturbation.
Dude 1: "Wow man, I had an amazing night thinking about your mom. I got spent nuts today."
Dude 2: "WTF?"
Dude 2: "WTF?"
by Wizards Sleeve November 19, 2005