The Collaborative International Dictionary of English v.0.48:

Wash drawing \Wash drawing\ (Art)
   In water-color painting, work in, or a work done chiefly in,
   washes, as distinguished from that done in stipple, in body
   color, etc.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

wash drawing
    n 1: a watercolor made by applying a series of monochrome washes
         one over the other [syn: wash, wash drawing]