(Applicable to males only)
To have been (usually unintentionally) struck very hard in the sensitive groin region, resulting in a large impact force upon the testicles. Symptoms include extreme pain between legs and doubling over, to being floored (if the impact is enough). Nadding is highly unpleasant. Any impact which does not draw a pained reaction of some kind was not a proper nadding, but probably a near miss or was simply too light to be considered a nadding.
An intentional strike upon the sensitive area is known as a low blow
Literal meaning: Not A Dud
NAD: (1) NADs are the opposite of DUDs. NADs don't like DUDs (Duds), don't hang out with DUDs, and definitely don't want to be DUDs. NADs do what they want, have fun, party hard, and believe that we are all only young once--so live it up now!
Kate: Are you going out tonight?
Alex: No, I am going to stay home by myself and hang out with my cat while you go out with our friends to a bar have fun.
Katie: I thought you were a NAD?
Alex: I guess I am a DUD.