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English definition of “insane”

insane

adjective     /ɪnˈseɪn/
C2 mentally ill: For the last ten years of his life he was clinically insane.informal I sometimes think I'm going insane (= I feel very confused).Of unsound mindStupid and silly C1 extremely unreasonable or stupid: It would be insane not to take advantage of this opportunity.Stupid and sillyOf unsound mind
(Definition of insane adjective from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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