pernicieux

French

pernicieux (feminine pernicieuse, masculine plural pernicieux, feminine plural pernicieuses)

(medicine, rare) insidious (having a slow and discreet, but dangerous evolution)
anémie pernicieuse ― pernicious anemia, or Biermer's anemia, a form of megaloblastic anemia due to vitamin B12 deficiency
fièvre pernicieuse ― pernicious fever (old term for neuro-malaria, the most serious form of malaria fever)
- 1879, Jules Verne, L'Île mystérieuse, Part 3, Chapter 10, translated by Stephen William White:
- Elle est insuffisante, répondit le reporter, et un troisième accès de fièvre pernicieuse qu’on ne coupe pas au moyen de la quinine est toujours mortel!
  [It] Is insufficient. And a third attack of pernicious fever, when one cannot break it by means of quinine, is always mortal!
(literary) morally harmful; pernicious
- 1715, Alain-René Lesage, Histoire de Gil Blas de Santillane, Book II, Chapter VII:
  Va, je t’abandonne aux gens qui te donnent de si pernicieux conseils.
  Go, I shall let you to those who give you such pernicious advice.
(dated) literally harmful or dangerous, usually of animals or persons
- 1699, François Fénelon, Les Aventures de Télémaque, Book 6, translated 1768 by John Hawkesworth:
  [S]ors aussi, pernicieux enfant: tu m’as fait plus de mal que lui!
  Depart thou also, pernicious boy! for my misfortunes are derived rather from thee than from him!