Definition of insidious in US English:

insidious

adjective

  • 1Proceeding in a gradual, subtle way, but with harmful effects.

    ‘sexually transmitted diseases can be insidious and sometimes without symptoms’
    • ‘The obstruction and harassment is subtle but insidious and seriously affects the ability of the aid agencies to do their job.’
    • ‘Slow calibration drift is a subtle and insidious source of unreliable instrument readings.’
    • ‘The onset is more insidious in brain tumors and the progress to vomiting is gradual.’
    • ‘This trade recession will be just as insidious in its effects as any market blowout.’
    • ‘It need by no means be obvious: it can be insidious and subtle.’
    • ‘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.’
    • ‘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.’
    • ‘Yet the incursions on free speech can be insidious and imperceptible.’
    • ‘But what makes this disease insidious is that in most cases it goes undetected until it's too late.’
    • ‘The more insidious problem that will remain is stacking the ballot paper in a deliberate attempt to increase the informal vote.’
    • ‘Significantly, even continuous low-level noise can be an insidious stressor.’
    • ‘The most insidious marketing comes from the baby food companies.’
    • ‘There was the slow, insidious change from fresh-faced beauty to freak.’
    • ‘Silently and stealthily this insidious, progressive disease has taken over.’
    • ‘Increases in childhood obesity and insidious health problems are, we suspect, linked to an increased consumption of junk food.’
    • ‘The propaganda is so insidious in the Murdoch press you can't even distinguish between news and opinion.’
    • ‘An offshoot of ventriloquist journalism, these are one of the more insidious forms of misinformation.’
    • ‘Their approach tends to be more subtle - and perhaps even more insidious.’
    • ‘The current ubiquity of advertising is certainly one of its most subtle and insidious properties.’
    • ‘Dyens eventually left France, feeling overwhelmed by what he saw as insidious, unspoken racism.’
    stealthy, subtle, surreptitious, sneaking, cunning, crafty, machiavellian, artful, guileful, sly, wily, tricky, slick, deceitful, deceptive, dishonest, underhand, backhanded, indirect
    View synonyms
    1. 1.1 Treacherous; crafty.
      ‘tangible proof of an insidious alliance’
      • ‘Even the insidious cane toad can't try and sneak through quarantine.’
      • ‘It harbours insidious designs in spite of its declared support for current Palestinian peace efforts.’
      • ‘But there's nothing laughable about the creature itself, a thoroughly insidious and hateful little beast.’
      • ‘Take up whatever insidious sport your smarmy boss has deemed ‘flavour of the month’.’
      • ‘The humanitarian argument is a particularly insidious one.’
      • ‘The more insidious the plot, the more difficult the cover up, and as the internet grows, so do the unanswered questions.’
      • ‘Carol Kane plays the insidious Madame Morrible as the evil twin of Mrs. Slocum from Are You Being Served?’
      • ‘I'd far rather go down in a face-to-face challenge, not after some insidious little campaign of back-biting.’
      • ‘His fast-talking portrayal of an insidious, damaged sexual predator is undoubtedly brilliant.’
      • ‘I learned that you have charged that your company is the victim of an insidious conspiracy masterminded by IBM.’
      • ‘They are, in my view, the most insidious of traitors.’
      • ‘What they do is insidious, evil, and downright mean to their addict-victims like my wife.’
      • ‘Personally, we can't stand this insidious practise of sneaking adverts into non-commercial formats.’
      • ‘And yet, the same argument reinvents itself time and again in all sorts of insidious avatars.’

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

/ɪnˈsɪdiəs//inˈsidēəs/