A person of low general intelligence.
"The editor labeled the young creationist an idiot before he could even argue his case against evolution."
A proponent of intelligent design.
In plain English: An idiot is someone who acts very foolishly and lacks common sense.
"He called his friend an idiot after he forgot their meeting time again."
idiotic, stupid
"Don't be such an idiot and forget to lock the door again."
The word "idiot" comes from the Ancient Greek term for a private citizen or layperson who lacked professional knowledge. It entered English via Old French and Middle English, originally describing anyone outside the educated elite rather than someone with severe intellectual disabilities as it does today.