Per‐ni″cious, a. [L. perniciosus, from pernicies destruction, from pernecare to kill or slay outright; per + necare to kill, slay: cf. F. pernicieux. Cf. Nuisance, Necromancy.] Having the quality of injuring or killing; destructive; very mischievous; baleful; malicious; wicked.
Let this pernicious hour
Stand aye accursed in the calendar. Shak.
Pernicious to his health. Prescott.
Syn. — Destructive; ruinous; deadly; noxious; injurious; baneful; deleterious; hurtful; mischievous.
— Per‐ni″cious‐ly, adv., — Per‐ni″cious‐ness, n.