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

In healthcare, for example, AI is being used in skin cancer detection, yet studies show that dermatologists are less likely to recommend biopsies for malignant skin cancers on patients with darker skin. —Pauleanna Reid, Forbes.com, 18 June 2025

One study found that overall incidence of malignant appendix tumors in the United States more than doubled from 2000 to 2016 — and the diagnosis increases were highest among younger age groups. —Tom Gavin, EverydayHealth.com, 10 June 2025

According to a GoFundMe page set up in her name, Phelan was eventually diagnosed with a grade 4 malignant brain tumor that was categorized as a glioma — a growth of cells that starts in the brain or spinal cord, according to the Mayo Clinic. —Charlotte Phillipp, People.com, 25 May 2025

Further testing turned out that the tumor was malignant. —Chris Hays, The Orlando Sentinel, 29 May 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