Extra stupid, more than really stupid, absolutely moronic, having a really low IQ, to be used when just plain stupid is not even close to describing how stupid someone or something is.
Guy 1: Last night a fly landed on my brothers crotch. He took the hardest swipe he could at it and totally nutted himself.
Guy 2: Unbelievable. Your brother iis industrial strength stupid.
Guy 1: My showoff neighbour changed the oil in his driveway on the weekend. He forgot to put the drain plug back in. He poured 5 quarts of oil, straight through his engine block all over his concrete. Then he hops in it, drives away and makes it to the end of the street before his engine seized.
Guy 2: Wow. That was a really industrial strength stupid thing to do. But since he's a douche, it's kind of funny.