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

An analysis of 1,000 tissue samples representing 11 major organs in just over 400 male donors has now delivered a clear map and expression profile of missing Y chromosomes in typical, pre-cancerous, and malignant tumors. — Mike McRae 20, New Atlas, 21 Sep. 2026

According to the National Cancer Institute, esophageal cancer is a disease in which malignant cancer cells form in the tissues of the esophagus. — Angeline Jane Bernabe, ABC News, 18 Sep. 2026

The analysis also revealed significant stroke risk elevations for adults diagnosed with bladder, stomach, and liver cancers, as well as myeloid leukemia and malignant brain and nervous system tumors. — Tom Gavin, EverydayHealth.com, 9 Sep. 2026

Perhaps the most intriguing risk factor for psychopathology gleaned from clinical psychological science, and one that is particularly relevant to the assessment and treatment of postpartum psychopathology, is malignant self-criticism. — Torie Bosch, STAT, 5 Sep. 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