insidious
/ɪnˈsɪdi.əs/
insidious adjective: causing harm in a stealthy, often gradual, manner.
Adjective
insidious (comparative more insidious, superlative most insidious)
- Causing harm in a stealthy, often gradual, manner.
- Strong and vigorous man as he looks, Livingstone has been for years the victim of a secret and insidious disease.1847, George Lippard, The Quaker City: or, The monks of Monk-Hall
- At some point in time they may become the source of an insidious cancer.1997, Matthew Wood, The book of herbal wisdom: using plants as medicine
- Synonyms:
- subtle
- Intending to entrap; alluring but harmful.
- Hansel and Gretel were lured by the witch’s insidious gingerbread house.
- Gashford slid his cold insidious palm into his master's grasp, and so, hand in hand, and followed still by Barnaby and by his mother too, they mingled with the concourse.1841 February–November, Charles Dickens, “Barnaby Rudge. Chapter 48.”, in Master Humphrey’s Clock, volume III, London: Chapman & Hall, […], →OCLC, page 215
- Treacherous.
- The battle was lost due to the actions of insidious defectors.
- But with whom do you contract that alliance? With the natural enemy of France — that insidious house of Austria — which detests our country from feeling, system, and necessity.1858, Phineas Camp Headley, The life of the Empress Josephine: first wife of Napoleon
- Synonyms:
- perfidious, proditorious, traitorous, booky, dastardly, disleal, disloyal, double-crossing, double-dealing, double-faced
insidious meaning in Tamil, Urdu, Bengali and Malayalam
insidious in Tamil
- தீங்கிழைக்கும், நயவஞ்சக, தீங்கிழைக்க, மெல்ல வளர்ச்சியுறும்
insidious in Urdu
- دغاباز, فریب کار, فریبی, غدار, مکار, پرفریب
insidious in Bengali
- ছলনাময়
insidious in Malayalam
- ഗൂഢമായി പടർന്നുപിടിക്കുന്ന, പ്രച്ഛന്നമായി മുന്നേറുന്ന, വഞ്ചകമായ
More languagesFewer languages
- insidious in Kannada
- ದ್ರೋಹದ, ಕಪಟದ, ಕೃತ್ರಿಮದ, ವಂಚನೆಯ
Examples of insidious in a sentence
- The nurse always must be alert to signs of slow leak or insidious infiltration.2007, Sharon Weinstein, Ada Lawrence Plumer, Principles and practice of intravenous therapy:
- The insidious whispers of the bad angel.1850, Nathaniel Hawthorne, chapter 5, in The Scarlet Letter, a Romance, Boston, Mass.: Ticknor, Reed, and Fields, →OCLC:
- The atmosphere of this insidious city comes out to meet him the moment he touches the European shore; for in London he meets Maria Gostrey just over from France.1969, Dorothy Brewster, John Angus Burrell, Dead reckonings in fiction:
- Without mincing words he would comment on his favorite theme, namely, the insidious scheme of the international Communists to conquer the free world.1983, James C. H. Shen, “Rejoining the Government”, in Robert Myers, editor, The U.S. & Free China: How the U.S. Sold Out Its Ally...
Synonyms of insidious
- subtle
- perfidious
- proditorious
- traitorous
- booky
- dastardly
- disloyal
- double-crossing
- double-dealing
- double-faced
30 more synonymsFewer synonyms
- double-hearted
- doublehearted
- faithless
- false
- false-hearted
- guileful
- hollow-hearted
- infidelitous
- Judaslike
- Judasly
- nonfaithful
- Punic
- ratlike
- recreant
- renegade
- reptilian
- traitorish
- traitorlike
- traitorly
- traitorsome
- treacherous
- treachersome
- unfaithful
- unleal
- unloyal
- unsteadfast
- untrue
- viperish
- viperous
- disleal
Forms of insidious
| comparative | more insidious |
|---|---|
| superlative | most insidious |
Origin of insidious
From Middle French insidieux, from Latin īnsidiōsus (“cunning, artful, deceitful”), from īnsidiae (“a lying in wait, an ambush, artifice, stratagem”) + -ōsus, from īnsideō (“to sit in or on”), from in (“in, on”) + sedeō (“to sit”).
Words formed from insidious
Words that rhyme with insidious
Questions about insidious
- What does insidious mean?
- Insidious means causing harm in a stealthy, often gradual, manner.
- What is insidious in Tamil?
- Insidious in Tamil is தீங்கிழைக்கும், நயவஞ்சக, தீங்கிழைக்க. See Insidious meaning in Tamil.
- How do you use insidious in a sentence?
- The nurse always must be alert to signs of slow leak or insidious infiltration.
- What part of speech is insidious?
- Insidious is an adjective.
- How do you pronounce insidious?
- Insidious is pronounced /ɪnˈsɪdi.əs/.
Words near insidious in the dictionary
Source and license
Adapted from Wiktionary: insidious (page history and authors); insidious (Tamil Wiktionary) (page history and authors); insidious (Urdu Wiktionary) (page history and authors); insidious (Bengali Wiktionary) (page history and authors); insidious (Malayalam Wiktionary) (page history and authors); insidious (Kannada Wiktionary) (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.
Last updated:
Pronunciation audio from Wikimedia Commons, each file under its own free license: LL-Q1860 (eng)-Wodencafe-insidious.wav.
Cite this entry: “insidious.” Word.ws, https://word.ws/insidious. Based on Wiktionary, CC BY-SA 4.0.