noun unfavorableness; evil nature.
2. malignancy ·noun the state of being a malignant.
3. malignancy ·noun virulence; tendency to a fatal issue; as, the malignancy of an ulcer or of a fever.
4. malignancy ·noun the state or quality of being malignant; extreme malevolence; bitter enmity; malice; as, malignancy of heart.