Definition of insidious in English:

insidious

adjective

  • Proceeding in a gradual, subtle way, but with very harmful effects.

    ‘sexual harassment is a serious and insidious problem’
    • ‘Yet the incursions on free speech can be insidious and imperceptible.’
    • ‘Dyens eventually left France, feeling overwhelmed by what he saw as insidious, unspoken racism.’
    • ‘The current ubiquity of advertising is certainly one of its most subtle and insidious properties.’
    • ‘Slow calibration drift is a subtle and insidious source of unreliable instrument readings.’
    • ‘There was the slow, insidious change from fresh-faced beauty to freak.’
    • ‘Significantly, even continuous low-level noise can be an insidious stressor.’
    • ‘The obstruction and harassment is subtle but insidious and seriously affects the ability of the aid agencies to do their job.’
    • ‘Silently and stealthily this insidious, progressive disease has taken over.’
    • ‘The propaganda is so insidious in the Murdoch press you can't even distinguish between news and opinion.’
    • ‘But what makes this disease insidious is that in most cases it goes undetected until it's too late.’
    • ‘It need by no means be obvious: it can be insidious and subtle.’
    • ‘An offshoot of ventriloquist journalism, these are one of the more insidious forms of misinformation.’
    • ‘Our sport is rife with that same insidious elitism that has decayed the core of other field sports, which now face the very real prospect of being outlawed.’
    • ‘Nuclear disc lesions are of gradual or insidious onset, the history may be on and off back pain for weeks and back pain getting worse.’
    • ‘The most insidious marketing comes from the baby food companies.’
    • ‘The more insidious problem that will remain is stacking the ballot paper in a deliberate attempt to increase the informal vote.’
    • ‘This trade recession will be just as insidious in its effects as any market blowout.’
    • ‘Their approach tends to be more subtle - and perhaps even more insidious.’
    • ‘The onset is more insidious in brain tumors and the progress to vomiting is gradual.’
    • ‘Increases in childhood obesity and insidious health problems are, we suspect, linked to an increased consumption of junk food.’
    stealthy, subtle, surreptitious, sneaking, cunning, crafty, machiavellian, artful, guileful, sly, wily, tricky, slick, deceitful, deceptive, dishonest, underhand, backhanded, indirect
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Origin

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

Pronunciation

insidious

/ɪnˈsɪdɪəs/