'Pernicious' definitions:

Definition of 'pernicious'

From: WordNet
adjective
Exceedingly harmful [syn: baneful, deadly, pernicious, pestilent]
adjective
Working or spreading in a hidden and usually injurious way; "glaucoma is an insidious disease"; "a subtle poison" [syn: insidious, pernicious, subtle]

Definition of 'Pernicious'

From: GCIDE
  • Pernicious \Per*ni"cious\, a. [L. pernix, -icis.] Quick; swift (to burn). [R.] --Milton. [1913 Webster]

Definition of 'Pernicious'

From: GCIDE
  • Pernicious \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. [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]