malignant
Americanadjective
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disposed to cause harm, suffering, or distress deliberately; feeling or showing ill will or hatred.
- Synonyms:
- malevolent, spiteful
- Antonyms:
- benign
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very dangerous or harmful in influence or effect.
- Synonyms:
- pernicious, hurtful, perilous
- Antonyms:
- benign
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Pathology.
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tending to produce death, as bubonic plague.
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(of a tumor) characterized by uncontrolled growth; cancerous, invasive, or metastatic.
- Antonyms:
- benign
-
adjective
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having or showing desire to harm others
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tending to cause great harm; injurious
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pathol (of a tumour) uncontrollable or resistant to therapy; rapidly spreading
noun
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Tending to have a destructive clinical course, as a malignant illness.
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Relating to cancer cells that are invasive and tend to metastasize. Malignant tumor cells are histologically more primitive than normal tissue.
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Compare benign
Usage
What’s the difference between malignant and benign? In a medical context, the word malignant is used to describe harmful masses or tumors that are cancerous and that grow and spread disease. The word benign is the opposite—it’s used to describe masses or tumors that are not cancerous (those that do not spread disease to other parts of the body). Both words are sometimes also used in general ways. Malignant can mean harmful or intended or intending to cause harm, while benign can mean kind, favorable, or gracious. The best clue to help remember their meanings is the prefix mal-, which means “bad” and shows up in a lot of other negative words, such as malfunction, malpractice, malicious, and maleficent. Here’s an example of malignant and benign used correctly in the same sentence. Example: She was afraid the lump was a malignant tumor, but it turned out to be a benign cyst—totally harmless. Want to learn more? Read the full breakdown of the difference between malignant and benign.
Discover More
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 term malignant is used in describing cancerous tumors (see cancer) because such growths are a threat to the health of the individual.
Other Word Forms
Etymology
Origin of malignant
First recorded in 1535–45; from Late Latin malignant-, stem of malignāns, present participle of malignāre “to act maliciously”; see malign, -ant
Explanation
For something that's very harmful, especially a tumor that's cancerous, use the term malignant. Malignant and its opposite benign are medical terms used to describe a tumor or growth as either cancerous or not respectively. The gn part of both words comes from the Latin word for born, but the word root mal means "evil," while bene means "kind." A malignant tumor grows uncontrollably and spreads to other parts of the body. Less commonly, malignant can also be used to mean "evil or malicious," like when someone has a malignant imagination.
Vocabulary lists containing malignant
Take the Bad with the Good: Bene and Mal
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"The Odyssey" by Homer, Books 1–7
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Beowulf
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
"This has implications for critical real-world scenarios, like when a radiologist can accurately classify masses on an X-ray as benign or malignant fairly automatically, often without extensive deliberation, thanks to years of training," Cox said.
From Science Daily ● Jul. 12, 2026
He takes no sensual pleasure in his destruction of Othello and Cassio, just the studied satisfaction of a sociopath watching with appreciation, as if from a distance, the malignant results of his handiwork.
From The Wall Street Journal ● Jul. 9, 2026
At the malignant end, you get the 1936 Berlin Olympics.
From Slate ● Jun. 25, 2026
Earlier this year, he disclosed that surgeons had successfully removed what he described as a "small, early-stage malignant tumour" from his prostate.
From Barron's ● Jun. 10, 2026
Just as environmental cancers are induced by a wide variety of chemical and physical agents, so the malignant condition itself is manifested in many different and biologically distinct ways.
From "Silent Spring" by Rachel Carson
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.