The Collaborative International Dictionary of English v.0.48:

Cyanosis \Cy`a*no"sis\ (s?`?-n?"s?s), n. [NL. See Cyanic.]
   (Med.)
   A condition in which, from insufficient a["e]ration of the
   blood, the surface of the body becomes blue. See
   Cyanopathy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cyanosis
    n 1: a bluish discoloration of the skin and mucous membranes; a
         sign that oxygen in the blood is dangerously diminished (as
         in carbon monoxide poisoning)