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

• malicious
• vicious
• cruel
• hateful
• nasty

Examples of malignant in a Sentence

a highly malignant form of cancer

a powerful and malignant influence

Recent Examples on the Web

There is no predicting what joke might set off this particular malignant narcissist in chief, so really, who’s to say who is next? —Lizz Winstead, Time, 27 Sep. 2025

Isabella received her diagnosis in October 2023 and underwent emergency surgery to remove a large medulloblastoma — a type of malignant tumor — in her cerebellum. —Vanessa Etienne, PEOPLE, 22 Sep. 2025

It has since been joined by Mosunetuzumab, Epcoritamab, and Glofitamab, all of which mobilize T cells against malignant B cells. —William A. Haseltine, Forbes.com, 18 Sep. 2025

Play it again, Towa Towa and the Guardians of the Sacred Tree follows the titular character, a priestess of Shinju Village, on a time-hopping quest to protect the realm from a malignant entity called Magatsu. —Christopher Cruz, Rolling Stone, 18 Sep. 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