The Collaborative International Dictionary of English v.0.48:

Fusain \Fu"sain"\, n. [F., the spindle tree; also, charcoal made
   from it.] (Fine Arts)
   (a) Fine charcoal of willow wood, used as a drawing
       implement.
   (b) A drawing made with it. See Charcoal, n. 2, and
       Charcoal drawing, under Charcoal.
       [1913 Webster]

WordNet (r) 3.0 (2006):

fusain
    n 1: a stick of black carbon material used for drawing [syn:
         charcoal, fusain]