The Collaborative International Dictionary of English v.0.48:

Chiaroscuro \Chia`ro*scu"ro\, Chiaro-oscuro \Chi*a"ro-os*cu"ro\,
   n. [It., clear dark.]
   (a) The arrangement of light and dark parts in a work of art,
       such as a drawing or painting, whether in monochrome or
       in color.
   (b) The art or practice of so arranging the light and dark
       parts as to produce a harmonious effect. Cf.
       Clair-obscur.
       [1913 Webster] Chiasm

WordNet (r) 3.0 (2006):

chiaroscuro
    n 1: a monochrome picture made by using several different shades
         of the same color