insidious

adjective

Definition of insidiousnext
as in treacherous
formal causing harm in a way that is gradual or not easily noticed Most people with this insidious disease have no idea that they are infected. an insidious enemy

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Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Recent Examples of insidious If anything, this makes those insidious Fridays insignificantly safer than the state average for the period. — Mike McRae 08, New Atlas, 8 Sep. 2026 Growing up in Beverly, Frates – the warrior against ALS who succumbed to the insidious disease in 2019 – was a huge fan of the Bruins’ star and had a poster of the defenseman in his room. — Steve Conroy, Boston Herald, 6 Sep. 2026 But the insidious harm that moves in the other direction — from illness, through a patient, into the person treating her — has no forum at all. — Jennifer Adaeze Okwerekwu, STAT, 1 Sep. 2026 When his insidious nature is revealed, the change in tone and his face gone malformed, the scene feels dynamic in a way that doesn’t require gore or intricate special effects. — Literary Hub, 28 Aug. 2026 See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
  1. treacherous
  2. subtle
  3. perfidious
  4. deceptive
  5. false
  6. misleading
  7. deceitful
  8. incorrect
Adjective
  • That, granted, was a brief if treacherous gut check, giving way to a re-expansion of valuations and a march to new highs through 2019 right up until Covid struck.
    — Michael Santoli, CNBC, 6 Oct. 2026
  • Taking the route around the Horn of Africa rather than going through the now-treacherous Bab el-Mandab Strait and on through the Suez Canal adds millions to overall costs.
    — David Faris, Washington Post, 5 Oct. 2026
Definition of treacherous
Adjective
  • Poindexter featured his three daughters in his first campaign advertisement for the general election, taking a subtle dig at Miller.
    — Lauren Green, The Washington Examiner, 7 Oct. 2026
  • Later still, we are introduced to Satoko Iijima (Ishida), who again shares many defining features with her two namesakes, albeit with just enough subtle differences to keep the audience on the back foot.
    — James Marsh, Variety, 7 Oct. 2026
Definition of subtle
Adjective
  • Logan Marshall-Green as Melanthius Melanthius is a perfidious goatherd who sides with Antinous.
    — Hannah Abraham, Forbes.com, 18 July 2026
  • This is perhaps the most perfidious practice of this sort of politics.
    — David M. Drucker, Twin Cities, 3 June 2026
Definition of perfidious
Adjective
  • In past elections, deceptive political robocalls have resulted in significant fines associated with the Telephone Consumer Protection Act, the federal law at the center of the petition.
    — ABC News, ABC News, 7 Oct. 2026
  • The film chronicled Gortner’s youth as a Pentecostal preacher in the American South and exposed the deceptive practices used to bilk believers out of their money.
    — Greg Evans, Deadline, 6 Oct. 2026
Definition of deceptive
Adjective
  • Some defendants face additional allegations involving false claims of citizenship or fraudulent statements that rest on separate federal statutes.
    — Antonio María Delgado, Miami Herald, 6 Oct. 2026
  • Those numbers include 759 false identification cards confiscated, 378 alcohol-possession-by-a-minor violations and 98 fake-ID citations during the calendar-year reporting period, according to Oxford Police.
    — Kelsie Cairns, FOXNews.com, 6 Oct. 2026
Definition of false
Adjective
  • The women, many of whom were first-time surrogates, say they were given misleading or incomplete information about the couple’s family situation and intentions.
    — ABC News, ABC News, 6 Oct. 2026
  • Low primary turnout can also lead to unexpected results – and these results can create misleading perceptions of the election.
    — Robert Boatright, The Conversation, 6 Oct. 2026
Definition of misleading
Adjective
  • Magpies are opportunistic scavengers, incredibly cunning and deceitful and capable of calculated deception.
    — Voice of the People, New York Daily News, 28 Sep. 2026
  • Bogus texts, mystery calls, deceitful emails all aimed at stealing your personal information and your money are relentless.
    — Donna Vickroy, Chicago Tribune, 13 Aug. 2026
Definition of deceitful
Adjective
  • That can include circumstances outside the property holder’s control or if the Controller’s Office gave them incorrect information.
    — Stephen Hobbs, Sacbee.com, 4 Oct. 2026
  • The company says its services can produce incorrect or incomplete information.
    — Kurt Knutsson, FOXNews.com, 3 Oct. 2026
Definition of incorrect

Browse Nearby Words

inside tracks
insidious
insidiously
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Cite this Entry

“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 9 Oct. 2026.

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