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 of malignant

• 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

Various types of cancer, in which malignant tumors invade surrounding tissues, contributed to between 13,000 and 20,000 deaths annually in this time frame. — Melissa Rudy, FOXNews.com, 3 July 2026

Asymptomatic lesions discovered incidentally in populations could also be monitored en masse to generate a robust database that would help researchers learn which types of lesions are more (or less) likely to turn malignant. — Paul Hsieh, Forbes.com, 30 June 2026

Cannon, who has 12 children, announced on a December 2021 episode of his talk show that Zen, his seventh child, had died of brain cancer, just three months after doctors discovered a malignant tumor and fluid building in his head. — Emlyn Travis, Entertainment Weekly, 26 June 2026

During that time, Carol faced a relapse of a malignant brain tumor, which had been diagnosed 7 years earlier at the age of 36. — Lexi Lane, PEOPLE, 13 June 2026

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