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Definition of insidious adjective from the Oxford Advanced Learner's Dictionary

insidious

adjective
 
/ɪnˈsɪdiəs/
 
/ɪnˈsɪdiəs/
(formal, disapproving)
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  1. spreading gradually or without being noticed, but causing serious harm
    • the insidious effects of polluted water supplies
    Oxford Collocations DictionaryInsidious is used with these nouns:
    • threat
    See full entry
    Word Originmid 16th cent.: from Latin insidiosus ‘cunning’, from insidiae ‘an ambush or trick’, from insidere ‘lie in wait for’, from in- ‘on’ + sedere ‘sit’.
See insidious in the Oxford Advanced American Dictionary
trait
noun
 
 
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