pernicious

pernicious
    adj 1: exceedingly harmful [syn: {baneful}, {deadly},
           {pernicious}, {pestilent}]
    2: working or spreading in a hidden and usually injurious way;
       "glaucoma is an insidious disease"; "a subtle poison" [syn:
       {insidious}, {pernicious}, {subtle}]
    

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

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.
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         Pernicious to his health.                --Prescott.
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   Syn: Destructive; ruinous; deadly; noxious; injurious;
        baneful; deleterious; hurtful; mischievous.
        [1913 Webster] -- {Per*ni"cious*ly}, adv., --
        {Per*ni"cious*ness}, n.
        [1913 Webster]
    

57 Moby Thesaurus words for "pernicious":
      baleful, baneful, brutal, corroding, corrosive, corrupting,
      corruptive, counterproductive, damaging, deadly, death-bringing,
      deathful, deathly, deleterious, destructive, detrimental,
      devastating, disadvantageous, disserviceable, distressing, fatal,
      feral, harmful, hurtful, injurious, internecine, killing, lethal,
      malefic, maleficent, malevolent, malign, malignant, miasmatic,
      miasmic, mischievous, mortal, noisome, noxious, ominous,
      pestiferous, pestilent, pestilential, poisonous, prejudicial,
      ruinous, savage, scatheful, sinister, swart, toxic, venenate,
      veneniferous, venenous, venomous, vicious, virulent