The Collaborative International Dictionary of English v.0.48:

Vitiligo \Vit`i*li"go\, n. [L., a kind of tetter, fr. vitium
   blemish, vice.] (Med.)
   A rare skin disease consisting in the development of smooth,
   milk-white spots upon various parts of the body.
   [1913 Webster]

WordNet (r) 3.0 (2006):

vitiligo
    n 1: an acquired skin disease characterized by patches of
         unpigmented skin (often surrounded by a heavily pigmented
         border)