pernicious

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. [ 1913 Webster ]

Let this pernicious hour
Stand aye accursed in the calendar. Shak. [ 1913 Webster ]

Pernicious to his health. Prescott. [ 1913 Webster ]

Syn. -- Destructive; ruinous; deadly; noxious; injurious; baneful; deleterious; hurtful; mischievous. [ 1913 Webster ]

-- Per*ni"cious*ly, adv., -- Per*ni"cious*ness, n. [ 1913 Webster ]