The Collaborative International Dictionary of English v.0.48:

Charcoal \Char"coal`\, n. [See Char, v. t., to burn or to
   reduce to coal, and Coal.]
   1. Impure carbon prepared from vegetable or animal
      substances; esp., coal made by charring wood in a kiln,
      retort, etc., from which air is excluded. It is used for
      fuel and in various mechanical, artistic, and chemical
      processes.
      [1913 Webster]

   2. (Fine Arts) Finely prepared charcoal in small sticks, used
      as a drawing implement.
      [1913 Webster]

   Animal charcoal, a fine charcoal prepared by calcining
      bones in a closed vessel; -- used as a filtering agent in
      sugar refining, and as an absorbent and disinfectant.

   Charcoal blacks, the black pigment, consisting of burnt
      ivory, bone, cock, peach stones, and other substances.

   Charcoal drawing (Fine Arts), a drawing made with charcoal.
      See Charcoal, 2. Until within a few years this material
      has been used almost exclusively for preliminary outline,
      etc., but at present many finished drawings are made with
      it.

   Charcoal point, a carbon pencil prepared for use in an
      electric light apparatus.

   Mineral charcoal, a term applied to silky fibrous layers of
      charcoal, interlaminated in beds of ordinary bituminous
      coal; -- known to miners as mother of coal.
      [1913 Webster] charcoal-gray

WordNet (r) 3.0 (2006):

charcoal
    adj 1: of a very dark grey [syn: charcoal, charcoal-grey,
           charcoal-gray]
    n 1: a carbonaceous material obtained by heating wood or other
         organic matter in the absence of air [syn: charcoal,
         wood coal]
    2: a stick of black carbon material used for drawing [syn:
       charcoal, fusain]
    3: a very dark grey color [syn: charcoal, charcoal grey,
       charcoal gray, oxford grey, oxford gray]
    4: a drawing made with a stick of black carbon material
    v 1: draw, trace, or represent with charcoal

Moby Thesaurus II by Grady Ward, 1.0:

138 Moby Thesaurus words for "charcoal":
   air brush, alcohol, art paper, ash, ashes, benzine,
   black and white, blackening, blacking, blackwash, brand, briquette,
   brouillon, brush, burnable, burnt cork, butane, calx,
   camera lucida, camera obscura, canvas, carbon, carbon black,
   cartoon, chalk, charcoal drawing, chiaroscuro, cinder, clinker,
   coal, coke, combustible, coom, crayon, crow, delineation, design,
   diagram, doodle, dope, draft, drafting, drawing, drawing paper,
   drawing pencil, drier, dross, easel, ebauche, ebon, ebony,
   esquisse, ethane, ethanol, fireball, firing, fixative, flammable,
   flammable material, fuel, fuel additive, fuel dope, fume, gas,
   gas black, gas carbon, gasoline, graph, ground, heptane, hexane,
   inflammable, inflammable material, ink, isooctane, jet, jet fuel,
   kerosene, lampblack, lava, lay figure, line drawing, maulstick,
   medium, methane, methanol, natural gas, night, octane, oil, paint,
   paintbrush, palette, palette knife, paraffin, pastel, peat,
   pen-and-ink, pencil, pencil drawing, pentane, pigments, pitch,
   propane, propellant, raven, reek, rocket fuel, rough copy,
   rough draft, rough outline, scoria, scratchboard, siccative,
   silhouette, silver-print drawing, sinopia, sketch, sketchbook,
   sketching, sketchpad, slag, sloe, smoke, smudge, smut, soot,
   spatula, spray gun, stove black, study, stump, sullage, tar,
   tracing, turf, varnish, vignette