Definition of "malignant" in English

adjective

1. Harmful, malevolent, injurious.

   • malignant temper; malignant revenge; malignant infection

2. (medicine) Tending to produce death; threatening a fatal issue.

   • malignant diphtheria
   • a malignant tumor

noun

1. A deviant; a person who is hostile or destructive to society.

2. (historical, derogatory, obsolete) A person who fought for Charles I in the English Civil War.