NOB is an insult word directed to an Idiot.
Itâs mainly used when someone does or says something completely and utterly idiotic, and you yell it at them in recoil of the stupid situation that just occurred.
Person 1: *Drops glass of water*
Person 1: âOh no! I dropped my glass of water! Now thereâs glass and water everywhere...â
Person 2: âOh my god, you NOB!â