ma·lig·nant / məˈlignənt/ • adj. 1. (of a disease) very virulent or infectious. ∎  (of a tumor) tending to invade normal tissue or to recur after removal; cancerous. Contrasted with benign.2. malevolent: in the hands of malignant fate.DERIVATIVES: ma·lig·nant·ly adv.

malignant (mă-lig-nănt) adj.
1. describing a tumour that invades and destroys the tissue in which it originates and has the potential to spread to other sites in the body. See cancer, metastasis.

2. describing any disorder that becomes life threatening if untreated. Compare benign.

Malignant a person who is disaffected towards constituted authority, a malcontent; especially (in Parliamentarian terminology), a supporter of the royalist cause during the English civil war. This may ultimately derive from established usage of the adjective in 16th-century Protestant polemic, as in the phrase Church malignant.

malignant Describing a mutant cell or group of cells that proliferates at a faster rate than normal cells and has the capacity to spread to other sites in the body. See cancer.