INSIDIOUS

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 Dictionary entry overview: What does insidious mean? 

• INSIDIOUS (adjective)
  The adjective INSIDIOUS has 3 senses:

1. beguiling but harmful

2. intended to entrap

3. working or spreading in a hidden and usually injurious way

  Familiarity information: INSIDIOUS used as an adjective is uncommon.

 Dictionary entry details 

• INSIDIOUS (adjective)

Sense 1

Meaning:

Beguiling but harmful

Context example:

insidious pleasures

Similar:

seductive (tending to entice into a desired action or state)

Derivation:

insidiousness (the quality of being designed to entrap)

Sense 2

Meaning:

Intended to entrap

Similar:

dangerous; unsafe (involving or causing danger or risk; liable to hurt or harm)

Derivation:

insidiousness (the quality of being designed to entrap)

Sense 3

Meaning:

Working or spreading in a hidden and usually injurious way

Synonyms:

insidious; pernicious; subtle

Context example:

a subtle poison

Similar:

harmful (causing or capable of causing harm)

Derivation:

insidiousness (subtle and cumulative harmfulness (especially of a disease))

 Context examples 

Most patients with chronic myelogenous leukemia are diagnosed in the chronic phase, which usually has an insidious onset and may last from several months to several years.

(Chronic Phase Chronic Myelogenous Leukemia, BCR-ABL1 Positive, NCI Thesaurus/WHO)

An insidious poorly circumscribed neoplasm arising from the deep soft tissues.

(Deep Fibromatosis/Desmoid Tumor, NCI Thesaurus)

An insidious poorly circumscribed neoplasm arising from the soft tissues outside the abdomen.

(Extraabdominal Fibromatosis, NCI Thesaurus)

The insidious revolt led by Buck had destroyed the solidarity of the team.

(The Call of the Wild, by Jack London)

It had sprung from the perch and was circling slowly round the Queen's Hall with a dry, leathery flapping of its ten-foot wings, while a putrid and insidious odor pervaded the room.

(The Lost World, by Sir Arthur Conan Doyle)

An insidious poorly circumscribed neoplasm arising from the deep soft tissues of the abdomen.

(Abdominal Fibromatosis, NCI Thesaurus)

I answer no such irrelevant and insidious questions; though were I to answer all that you could put in the course of an hour, you would never be able to prove that it was not Thornton Lacey—for such it certainly was.

(Mansfield Park, by Jane Austen)

At this moment, an ingenious and animating suspicion entering Emma's brain with regard to Jane Fairfax, this charming Mr. Dixon, and the not going to Ireland, she said, with the insidious design of farther discovery, You must feel it very fortunate that Miss Fairfax should be allowed to come to you at such a time.

(Emma, by Jane Austen)

She meant to take her in the carriage, leave her at the Abbey Mill, while she drove a little farther, and call for her again so soon, as to allow no time for insidious applications or dangerous recurrences to the past, and give the most decided proof of what degree of intimacy was chosen for the future.

(Emma, by Jane Austen)

Mr. Crawford was no longer the Mr. Crawford who, as the clandestine, insidious, treacherous admirer of Maria Bertram, had been her abhorrence, whom she had hated to see or to speak to, in whom she could believe no good quality to exist, and whose power, even of being agreeable, she had barely acknowledged.

(Mansfield Park, by Jane Austen)