1. Pertaining to a disease that is characterized by extreme virulence and is exceptionally contagious or infectious: As a patient, Leroy was placed in the isolation ward as a result of the extremely malignant nature of his lung infection.
2. A reference to the tendency of becoming worse and the resistance to medical treatment; pertaining to cancerous development: Given the malignant nature of the growth in the Bill's stomach, the doctor was recommending radical surgery.
3. Relating to or referring to a threat to produce death; harmful; virulent: The term malignant primarily describes such ailments as a tumor which spreads from its original location to affect other areas of the body with potentially life-threatening results.
4. Characterized by an intense ill-will; keenly desirous of the suffering or misfortune of others generally: The dictator had a powerful and malignant influence on the lives of the citizens of his nation and that's why so many of them fled to neighboring countries.