malignant

adjective

ma·​lig·​nant mə-ˈlig-nənt 

1

: tending to produce death or deterioration

malignant malaria

especially : tending to infiltrate, metastasize, and terminate fatally

a malignant tumor

2

a

: evil in nature, influence, or effect : injurious

a powerful and malignant influence

b

: passionately and relentlessly malevolent : aggressively malicious

the malignant tongues of gossipers

c

obsolete : malcontent, disaffected

malignantly adverb

Synonyms

• bad [slang]
• bitchy
• catty
• cruel
• despiteful
• hateful
• malevolent
• malicious
• malign
• mean
• nasty
• spiteful
• vicious
• virulent

Examples of malignant in a Sentence

a highly malignant form of cancer

a powerful and malignant influence

Recent Examples on the Web

Last month, my son reached two years in remission from a rare, malignant cancer that almost took his eye and his life. —Dayna Copeland, The Mercury News, 15 Mar. 2025

After a series of tests, Karen was diagnosed with a glioma of the pons, a malignant tumor growing within the middle part of her brain stem. —Jackie Tempera, People.com, 27 Apr. 2025

In 2024, Tina Knowles, 71, underwent a lumpectomy to have the malignant tumor removed. —Sara Vallone, Miami Herald, 22 Apr. 2025

Based on breast imaging, AI tools can be used to better predict if a lesion is malignant and support clinical decision making. —Eyal Shamir, Forbes, 14 Mar. 2025

Word History

Etymology

Late Latin malignant-, malignans, present participle of malignari

First Known Use

1542, in the meaning defined at sense 2c

Phrases Containing malignant

• malignant melanoma

Rhymes for malignant

• indignant
• nonmalignant
• premalignant

Kids Definition

malignant

adjective

ma·​lig·​nant mə-ˈlig-nənt 

1

: evil in influence or effect : injurious

2

: malicious sense 1

3

: tending to produce death

malignant tumors

malignantly adverb

Medical Definition

malignant

adjective

ma·​lig·​nant mə-ˈlig-nənt 

1

: tending to produce death or deterioration

malignant malaria

especially : tending to infiltrate, metastasize, and terminate fatally

malignant tumors

compare benign sense 1

2

: of unfavorable prognosis : not responding favorably to treatment

psychotic reactions with a malignant trend