/ ˌpærəˈnɔɪə; NAmE / noun [ U ]
1.
( medical ) a mental illness in which a person may wrongly believe that other people are trying to harm them, that they are sb very important, etc.
2.
( informal ) fear or suspicion of other people when there is no evidence or reason for this
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WORD ORIGIN
early 19th cent.: modern Latin , from Greek , from paranoos distracted, from para irregular + noos mind.