adj. - Something stupefying, generally used in a positive fashion. Used to denote a level of something so enormous, it's ridiculous almost to the point of being stupid.
Also used as an adv., it is less ubiquitously positive when found in this form.
You check that cat on the sax? He's so good it's stupidacious!
Occurring unexpectedly or unintentionally after doing something so stupid, careless or negligent that it should have been obvious that you would run into trouble.
The officer stupidentally shot three other officers while trying to stop a pit bull that was attacking them.