(1):

(n.) The state or quality of being malignant; extreme malevolence; bitter enmity; malice; as, malignancy of heart.

(2):

(n.) Unfavorableness; evil nature.

(3):

(n.) Virulence; tendency to a fatal issue; as, the malignancy of an ulcer or of a fever.

(4):

(n.) The state of being a malignant.