The Collaborative International Dictionary of English v.0.48:

Guereza \Gue*re"za\, n. (Zool.)
   A beautiful Abyssinian monkey (Colobus guereza), having the
   body black, with a fringe of long, silky, white hair along
   the sides, and a tuft of the same at the end of the tail. The
   frontal band, cheeks, and chin are white.
   [1913 Webster]

WordNet (r) 3.0 (2006):

guereza
    n 1: a colobus monkey with a reddish brown coat and white silky
         fringes down both sides of the body [syn: guereza,
         Colobus guereza]