I like this quote:

     With a stupid person all this is absolutely impossible as explained by the Third Basic Law. A stupid creature will harass you for no reason, for no advantage, without any plan or scheme and at the most improbable times and places. You have no rational way of telling if and when and how and why the stupid creature attacks. When confronted with a stupid individual you are completely at his mercy.

(the reader cries in despair)

"A stupid person is a person who causes losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses."

Yeah, this lines up with my personal description of stupid: incapable of achieving one's own goals because of stubbornness, mean-spiritedness, pride, persistent misunderstanding, inability or unwillingness to learn. A danger to themself and others. Usually and unfortunately coupled with overconfidence.

This is stark contrast to being merely ignorant (lacking knowledge, naive or sheltered) and dumb (incapable of learning or grasping complex subjects).

Ignorance is generally fixable and with some capacity, dumbness too. But stupidity is a special kind of bad.

I think we're well served by distinct language:

  * "intelligent" is the intellectual capacity one is born with
  * "stupid" is the failure to use that intellectual capacity

I know plenty of very intelligent people who have been quite stupid at times. I know that while I may have adequate intelligence I've certainly been stupid more than once (or maybe even twice).