Definition of "vicious"

vicious

/ˈvɪʃəs/

adjective
comparative more vicious or viciouser, superlative most vicious or viciousest
1. Violent, destructive and cruel.
2. Savage and aggressive.
  Quotations
  He had always been remarkably immune from such little ailments, and had only once in his life been ill, of a vicious pneumonia long ago at school. He hadn't the faintest idea what to with a cold in the head, he just took quinine and continued to blow his nose.
  1922, Michael Arlen, “2/9/1”, in “Piracy”: A Romantic Chronicle of These Days
3. (archaic) Pertaining to vice; characterised by immorality or depravity.
  Quotations
  We may so seize on vertue, that if we embrace it with an over-greedy and violent desire, it may become vicious.
  1603, Michel de Montaigne, translated by John Florio, The Essayes […], London: […] Val[entine] Simmes for Edward Blount […]