A kick aimed at the male genital region, executed at such a slow speed, and at such a low angle, that it eludes the victim's peripheral vision and defensive reflex.
As such, the victim is often unable to dodge or block the kick, jump out of range, or squeeze his legs together to neutralize the attack.
"Dude, Ryan hit me with the slow nut kick just now. Didn't see that shit coming until it was too late! Shit was devastating!!!"