MALIG'NANCY, n. [See Malignant.] Extreme malevolence; bitter enmity; malice; as malignancy of heart.

1. Unfavorableness; unpropitiousness; as the malignancy of the aspect of planets.

The malignancy of my fate might distemper yours.

2. Virulence; tendency to mortification or to a fatal issue; as the malignancy of an ulcer or of a fever.