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English definition of “insidious”


adjective    /ɪnˈsɪd·i·əs/
(of something unpleasant or dangerous ) gradually and secretly causing harm : Cancer is an insidious disease . insidiously    /ɪnˈsɪd·i·əs·li/ adverb His negative attitude slowly and insidiously spoiled the atmosphere around the office .
(Definition of insidious adjective from the Cambridge Academic Content Dictionary © Cambridge University Press)
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