adj. 1 a (of a disease) very virulent or infectious (malignant cholera). b (of a tumour) tending to invade normal tissue and recur after removal; cancerous. 2 harmful; feeling or showing intense ill will. malignant pustule a form of anthrax. malignancy n. (pl. -ies). malignantly adv.
[ LL malignare (as MALIGN) ]