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

The patient was selected because his condition, unlike cancers such as leukemia, did not carry the risk of reimplanting malignant cells along with the transplant that could lead to a recurrence. — Adam Kovac, Scientific American, 23 July 2026

That’s the day Prigge was diagnosed with a malignant brain tumor, an aggressive form of cancer. — Amy Wenk, AJC.com, 22 July 2026

Per the Mayo Clinic, glioblastomas are the most serious type of glioma brain tumor and are the most common malignant brain tumor in adults. — Adam England, PEOPLE, 16 July 2026

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

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