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’
    • ‘It need by no means be obvious: it can be insidious and subtle.’
    • ‘The obstruction and harassment is subtle but insidious and seriously affects the ability of the aid agencies to do their job.’
    • ‘The most insidious marketing comes from the baby food companies.’
    • ‘This trade recession will be just as insidious in its effects as any market blowout.’
    • ‘There was the slow, insidious change from fresh-faced beauty to freak.’
    • ‘But what makes this disease insidious is that in most cases it goes undetected until it's too late.’
    • ‘An offshoot of ventriloquist journalism, these are one of the more insidious forms of misinformation.’
    • ‘Silently and stealthily this insidious, progressive disease has taken over.’
    • ‘Yet the incursions on free speech can be insidious and imperceptible.’
    • ‘The more insidious problem that will remain is stacking the ballot paper in a deliberate attempt to increase the informal vote.’
    • ‘The onset is more insidious in brain tumors and the progress to vomiting is gradual.’
    • ‘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.’
    • ‘Increases in childhood obesity and insidious health problems are, we suspect, linked to an increased consumption of junk food.’
    • ‘Dyens eventually left France, feeling overwhelmed by what he saw as insidious, unspoken racism.’
    • ‘Their approach tends to be more subtle - and perhaps even more insidious.’
    • ‘Slow calibration drift is a subtle and insidious source of unreliable instrument readings.’
    • ‘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 current ubiquity of advertising is certainly one of its most subtle and insidious properties.’
    • ‘The propaganda is so insidious in the Murdoch press you can't even distinguish between news and opinion.’
    • ‘Significantly, even continuous low-level noise can be an insidious stressor.’
    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/