malignant

/məˈlɪgnənt/

/məˈlɪgnɪnt/

For something that's very harmful, especially a tumor that's cancerous, use the term malignant.

Malignant and its opposite benign are medical terms used to describe a tumor or growth as either cancerous or not respectively. The gn part of both words comes from the Latin word for born, but the word root mal means "evil," while bene means "kind." A malignant tumor grows uncontrollably and spreads to other parts of the body. Less commonly, malignant can also be used to mean "evil or malicious," like when someone has a malignant imagination.

Definitions of malignant

1. adjective

   dangerous to health; characterized by progressive and uncontrolled growth (especially of a tumor)
   synonyms:

   cancerous

   relating to or affected with abnormal cell growth

   antonyms:

   benign

   not dangerous to health; not recurrent or progressive (especially of a tumor)
2. adjective

   showing malicious ill will and a desire to hurt; motivated by spite
   synonyms: despiteful, spiteful, vindictive

   malicious

   having the nature of or resulting from malice