|—J.R. "Bob" Dobbs, Church of the SubGenius|
Stupidity, as defined by Answers.com, is "The quality or condition of being stupid."  What did you think it meant? Duh! Synonyms include feeble-mindedness, imbecility, idiocy, brainlessness, ineptitude, muddleheadedness, slow-wittedness, doltishness, and nitwittedness.
Sadly most acts of stupidity make perfect sense to the person committing them.
Intelligence and stupidity are not in any way incompatible. Indeed, really profound stupidity takes some intelligence to pull off.
 Stupid laws
 The basic laws of human stupidity
- Main article: The basic laws of human stupidity
Cipolla's five laws of stupidity :
- We always underestimate the number of stupid people.
- The probability of a person being stupid is independent of any other characteristic of that person.
- A stupid person is someone who causes damage to another person, or a group of people, without any advantage accruing to himself (or herself) — or even with some resultant self-damage.
- Non-stupid people always underestimate the damaging power of stupid people. They constantly forget that at any moment, and in any circumstance, associating with stupid people invariably constitutes an expensive mistake.
- A stupid person is the most dangerous person in existence.
 Hanlon's razor
Hanlon's razor recommends, "Never attribute to malice that which can be adequately explained by stupidity."
 Dunning-Kruger effect
"I see stupid people ... and they don't know they're stupid!"
 Examples of stupidity documented on RationalWiki
- Rapture (rapture services)--"All this for the princely sum of $40 a year, which is a paltry price to pay for confirmation of one's Utter Stupidity."
- Evolutionist--"Some creationists even argue that 'evolutionism' is a secular religion to compound this stupidity."
- Holocaust denial--"This is manifested in some of the aims of Holocaust denial (stupidity and hatred not mentioned)."
- Agnostic Atheism Wager--"This does tend to point out the stupidity of religious dogma, and lead one to a secular attempt to determine 'how we should live'."
- Birth control--"Cynically put, stupidity - at least with respect to fucking everything in sight - reigns supreme in the world of natural selection."
- 101 evidences for a young age of the earth and the universe--"To say then that the outliers and unexplained should take precedent over the weight of evidence is the height of arrogance and stupidity."
 Stupid quotes
It is infuriating to be quoted again and again by creationists-whether through design or stupidity, I do not know-as admitting that the fossil record includes no transitional forms.--Stephen Jay Gould, "Evolution as Fact and Theory," Discover, May 1981 
It is against stupidity in every shape and form that we have to wage our eternal battle. But how can we wonder at the want of sense on the part of those who have had no advantages, when we see such plentiful absence of that commodity on the part of those who have had all the advantages?--William Booth 
Only two things are infinite, the universe and human stupidity, and the universe I am not so sure.--Albert Einstein
- Think about it... half the people you meet are stupider than the other half. And they are probably in charge.