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  1. disposed to cause harm, suffering, or distress deliberately; feeling or showing ill will or hatred.
  2. very dangerous or harmful in influence or effect.
  3. Pathology.
    1. tending to produce death, as bubonic plague.
    2. (of a tumor) characterized by uncontrolled growth; cancerous, invasive, or metastatic.

Origin of malignant

1535–45; < Late Latin malignant- (stem of malignāns), present participle of malignāre to act maliciously. See malign, -ant
Related formsma·lig·nant·ly, adverbnon·ma·lig·nant, adjectivenon·ma·lig·nant·ly, adverbsem·i·ma·lig·nant, adjectivesem·i·ma·lig·nant·ly, adverbun·ma·lig·nant, adjectiveun·ma·lig·nant·ly, adverb

Synonyms for malignant

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Antonyms for malignant

1–3. benign. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for malignant

Contemporary Examples of malignant

Historical Examples of malignant

  • The forger smiled, and there was malignant triumph in his expression.

    Within the Law

    Marvin Dana

  • The pursuit had a malignant pleasure in it: we knew the men we were driving before us.

    In the Valley

    Harold Frederic

  • His malignant and revengeful passions were not so easily laid.

  • You are a most malignant and dangerous Whig to have so far drawn them from their duty.'

    Micah Clarke

    Arthur Conan Doyle

  • Into his snarl he incorporated all that was vicious, malignant, and horrible.

    White Fang

    Jack London

British Dictionary definitions for malignant


  1. having or showing desire to harm others
  2. tending to cause great harm; injurious
  3. pathol (of a tumour) uncontrollable or resistant to therapy; rapidly spreading
  1. history (in the English Civil War) a Parliamentarian term for a royalist (def. 1)
Derived Formsmalignantly, adverb

Word Origin for malignant

C16: from Late Latin malīgnāre to behave spitefully, from Latin malīgnus malign
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for malignant

1560s, in reference to diseases, from Middle French malignant and directly from Late Latin malignantem (nominative malignans) "acting from malice," present participle of malignare "injure maliciously" (see malign (v.)). Earlier in the church malignant "followers of the antichrist," from Latin ecclesiam malignantum in early Church writing, applied by Protestant writers to the Church in Rome (1540s). As an adjective, Middle English used simple malign (early 14c.). Related: Malignantly.

Online Etymology Dictionary, © 2010 Douglas Harper

malignant in Medicine


  1. Threatening to life, as a disease; virulent.
  2. Tending to metastasize; cancerous. Used of a tumor.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

malignant in Science


  1. Tending to have a destructive clinical course, as a malignant illness.
  2. Relating to cancer cells that are invasive and tend to metastasize. Malignant tumor cells are histologically more primitive than normal tissue. Compare benign.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

malignant in Culture


A descriptive term for things or conditions that threaten life or well-being. Malignant is the opposite of benign.


The term malignant is used in describing cancerous tumors (see cancer) because such growths are a threat to the health of the individual.


The term is often used in a general way to denote something that is both destructive and fast growing: “The malignant growth of the suburbs is destroying the landscape.”
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.