INSIDIOUS


Meaning of INSIDIOUS in English

/ ɪnˈsɪdiəs; NAmE / adjective

( formal , disapproving ) spreading gradually or without being noticed, but causing serious harm :

the insidious effects of polluted water supplies

►  in·sidi·ous·ly adverb

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WORD ORIGIN

mid 16th cent.: from Latin insidiosus cunning, from insidiae an ambush or trick, from insidere lie in wait for, from in- on + sedere sit.

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.