'Perniciously' definitions:

Definition of 'perniciously'

From: WordNet
adverb
In a harmfully insidious manner; "these drugs act insidiously" [syn: insidiously, perniciously]
adverb
In a noxiously baneful way; "this banefully poisoned climate" [syn: banefully, perniciously]

Definition of 'Perniciously'

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]