1 usually offensive : a person affected with extreme mental retardation 2: a foolish or stupid person
Back to the controversial words. It's a penny word, though. Gets thrown around a lot, gets objected to a lot.
More specific than:
Idiot has a medical definition, yes, and it gets so over-used that its impact is pretty dilute unless you hit somebody who's in a position to be offended by it. So it's a less specific word with very specific underpinnings.
The medical definition is an IQ of under 30. Though the whole concept of "IQ" is fraught with its own problems...
Somehow the adjective stupid has dodged the offensive label. Not sure how it did that -- or is it just me? Idiot and moron are shades of the same thing, I think, whereas fool is less about intelligence and more about behavior or wisdom. Which is worse: idiot or moron? The former sounds a little sharper, thanks to the d and the t, and the latter draws out more because of the two o's. So maybe moron comes across just a little dumber and more insulting.
What comes to your mind? Does intelligence-based insulting offend you? How do your characters insult each other?