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

However, the author wants readers to see that displacement of many kinds, malignant or benign, can have far-reaching consequences — and sometimes those can be overcome. — Bethanne Patrick, Los Angeles Times, 2 Nov. 2026

Leo’s participation is complicated by his recent lung cancer diagnosis and surgery to remove a lower lobe of his right lung, which had a malignant tumor on it. — Colleen Kane, Chicago Tribune, 30 Oct. 2026

These early sequences display a keen ability from Matsumura to paint a tragic picture of malignant, festering grief from a past tragedy, without the need for any overt explanation. — James Marsh, Variety, 29 Oct. 2026

Cancer can exploit molecular signals that restrain immune responses, allowing malignant cells to escape attack even when identified. — Mike McRae 25, New Atlas, 26 Oct. 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