MALIG'NANCY, noun [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.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI