Source : Webster's Revised Unabridged Dictionary (1913)

Pityriasis \Pit`y*ri"a*sis\, n. [NL., fr. Gr. ?, fr. ?, lit.,
   bran.] (Med.)
   A superficial affection of the skin, characterized by
   irregular patches of thin scales which are shed in branlike
   particles.

   {Pityriasis versicolor} [NL.] (Med.), a parasitic disease of
      the skin, characterized by the development of reddish or
      brownish patches.