/ ˈɪdiət; NAmE / noun
1.
( informal ) a very stupid person
SYN fool :
When I lost my passport, I felt such an idiot.
Not that switch, you idiot!
2.
( old-fashioned , offensive ) a person with very low intelligence who cannot think or behave normally
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WORD ORIGIN
Middle English (denoting a person of low intelligence): via Old French from Latin idiota ignorant person, from Greek idiōtēs private person, layman, ignorant person, from idios own, private.