The Meaning of Insidious: What It Is and How To Use It

Do you know the definition of insidious? This article will provide you with all of the information you need on the word insidious, including its definition, usage, word origin, example sentences, and more!

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What does the word insidious mean?

According to sources like American Heritage Unabridged Dictionary of the English Language and Collins English Dictionary, the word insidious is an adjective that means harmful, dangerous or evil, or cunning in an injurious way like an ambush. The word insidious is four syllables – in-sid-i-ous, and the pronunciation of insidious is ɪnˈsɪdɪəs. The adverb form of insidious is formed by adding the suffix ly to create insidiously (adv.) Many things can be insidious, like an insidious disease or insidious illness like glaucoma, insidious enemy, insidious problems, an insidious rumor, insidious plot, insidious change that has a gave effect, an evil, insidious plan, insidious ways, an insidious drug or chemicals, an insidious liking, insidious side effects, insidious arts, an insidious onset, an insidious foe, insidious misinformation, an insidious witch, insidious trend, insidious form of water pollution, and more. 

There are many different languages that use words that mean insidious. You may notice that sometimes different languages have words that are very close to English words or to words of other languages. This is usually because the words share a root or origin. Often, cognates, which are words that look, sound, and mean something similar across languages, are formed when words share an origin. This list of translations for the word insidious is provided by Word Sense.

  •  Polish: podstępny‎, zdradliwy‎, zdradziecki‎
  •  Romanian: insidios‎
  •  Khmer: ដែលបញ្ឆោត‎ (dael bɑɲcʰaot)
  •  Serbo-Croatian: škodljiv‎, шкодљив‎
  •  Portuguese: insidioso‎
  •  Maori: toropuku‎
  •  Finnish: salakavala‎
  •  Armenian: նենգ‎
  •  Swedish: försåtlig‎
  •  Russian: скры́тый‎, кова́рный‎
  •  Spanish: insidioso‎
  •  French: insidieux‎
  •  Dutch: sluipend‎, verraderlijk‎

How can the word insidious be used in a sentence?

The word insidious can be used in many different sentences in the English language. Using words in a sentence is a great way to memorize their definitions. You can also try making quizzes for yourself or testing yourself with flashcards. Try using this word of the day in a sentence today! Below are several examples of insidious.

The insidious censorship of the press can cause serious harm as the problem spreads. The pay gap in the industry was insidious as well, but the leaders brushed it off in a harmless way.

Gretel and Hansel made their was to the witch’s insidious gingerbread house. 

They found five insidious decigrams of malourea in the cachet, which is known as the trade name Veronal.

David Glass insidiously tried to sabotage the vocals on Christianna and Barry Galvin’s 5th full-length album. 

The insidious professor at Princeton University used treachery and deceit to do great damage to the school, and his stratagem was to seem like his actions were all being taken in a harmless manner. 

The varroa mite, or Varroa destructor, was insidiously dangerous to the building.

The interval was insidious to the human ears, while inaudible since the range bottoms out at 20 Hz.

What is the origin of the word insidious?

According to Etymonline, the word insidious has been used since the 1540s. This word comes from France as the Middle French insidieux, which comes from the Latin insidiae insidēre/insidere sedēre and the derivative of insidēre, which is the Latin insidiosus/Latin īnsidiōsus/Latin insidiōsus cunning which uses the Latin suffix ōsus. This word comes from Indo-European roots.

What are synonyms and antonyms of insidious?

There are a variety of different words that one can use in place of the word insidious. These are called synonyms, which are words and phrases that have the same or a similar meaning as another word or phrase. Synonyms are useful to know if you are trying to expand your vocabulary as well as if you are trying to avoid repeating yourself. This list of synonyms for the word insidious is provided by Power Thesaurus.

  •  furtive
  •  all-inclusive
  •  evil
  •  playing politics
  •  delusory
  •  all-around
  •  dangerous
  •  deceptive
  •  all-encompassing
  •  machiavellian
  •  abundant
  •  faking one out
  •  vulpine
  •  plotting
  •  all-pervasive
  •  shifty
  •  delusive
  •  sneaking
  •  fallacious
  •  obliquitous
  •  disingenuous
  •  playing games
  •  arch
  •  elusive
  •  across-the-board
  •  slick
  •  accepted
  •  astute
  •  sinister
  •  double-dealing
  •  crooked
  •  puckish
  •  cunning
  •  duplicitous
  •  all-pervading
  •  double-crossing
  •  canny
  •  traitorous
  •  sly
  •  calculating
  •  pandemic
  •  foxy
  •  tricksy
  •  clever
  •  hypocritical
  •  stealthy
  •  secret
  •  all-in
  •  vipery
  •  treacherous
  •  deceiving
  •  crafty
  •  snaky
  •  unethical
  •  illusive
  •  subtlest
  •  jesuitical
  •  subtle
  •  all
  •  surreptitious
  •  artful
  •  deep
  •  designing
  •  all-over
  •  two-faced
  •  shrewd
  •  fraudulent
  •  dishonorable
  •  two-timing
  •  illusory
  •  wily
  •  slippery
  •  perfidious
  •  absolute
  •  mischievous
  •  pernicious
  •  false
  •  indirect
  •  sneaky
  •  devious
  •  guileful
  •  subtile
  •  smooth
  •  perilous
  •  beguiling
  •  tricky
  •  scheming
  •  all-out
  •  subtler
  •  deceitful
  •  sharp
  •  all-embracing
  •  not straightforward
  •  corrupt
  •  underhand
  •  shady
  •  serpentine
  •  underhanded
  •  unscrupulous
  •  dishonest

There are also numerous words and phrases that are antonyms for the word insidious. Antonyms are words and phrases that have the opposite meaning as another word or phrase. Opposite words are helpful to know if you are trying to expand your knowledge of the English language. This list of antonyms is provided by Power Thesaurus as well.

  •  straight
  •  conspicuous
  •  unconcealed
  •  artless
  •  up front
  •  open
  •  as pure as the driven snow
  •  insignificant
  •  frankish
  •  limited
  •  totally open
  •  straight to the point
  •  miniature
  •  upright
  •  white
  •  direct
  •  unbeguileful
  •  outspoken
  •  partial
  •  rudimentary
  •  pretenseless
  •  minimal
  •  poor
  •  deficient
  •  honest
  •  meager
  •  plain
  •  inadequate
  •  minor
  •  narrow
  •  up-front
  •  paltry
  •  talking turkey
  •  export-processing
  •  as good as your word
  •  frankhearted
  •  candid
  •  frank
  •  franco
  •  restricted
  •  undissimulated
  •  undissembling
  •  lean
  •  laid on the line
  •  scanty
  •  square-shooting
  •  straight-from-the-shoulder
  •  compact
  •  lay it on the line
  •  genuine
  •  harmless
  •  diminished
  •  insubstantial
  •  all wool and a yard wide
  •  sincere
  •  aboveboard
  •  guilt-free
  •  sparse
  •  miserly
  •  plain-dealing
  •  summary
  •  unvarnished
  •  person-to-person
  •  scant
  •  meagre
  •  forthright
  •  little
  •  ingenuous
  •  exclusive
  •  small
  •  incomplete
  •  guileless
  •  insufficient
  •  unequivocal
  •  circumscribed
  •  slight
  •  determinate
  •  tiny
  •  finite
  •  fair
  •  undisguised
  •  undissembled
  •  franc
  •  unsatisfactory
  •  realest
  •  reduced
  •  veracious
  •  straightforward
  •  basic
  •  brief
  •  short
  •  uncomprehensive
  •  truthful
  •  obvious

Overall, the word insidious means dangerously evil and cunning. This word is Latin in origin.


  1. Insidious definition and meaning | Collins English Dictionary
  2. Insidious synonyms – 557 Words and Phrases for Insidious | Power Thesaurus 
  3. Insidious antonyms – 94 Opposites of Insidious | Power Thesaurus 
  4. insidious | Origin and meaning of insidious | Online Etymology Dictionary