Source : Webster's Revised Unabridged Dictionary (1913)

Shading \Shad"ing\, n.
   1. Act or process of making a shade.

   2. That filling up which represents the effect of more or
      less darkness, expressing rotundity, projection, etc., in
      a picture or a drawing.

Shade \Shade\, v. t. [imp. & p. p. {Shaded}; p. pr. & vb. n.
   {Shading}.]
   1. To shelter or screen by intercepting the rays of light; to
      keep off illumination from. --Milton.

            I went to crop the sylvan scenes, And shade our
            altars with their leafy greens.       --Dryden.

   2. To shelter; to cover from injury; to protect; to screen;
      to hide; as, to shade one's eyes.

            Ere in our own house I do shade my head. --Shak.

   3. To obscure; to dim the brightness of.

            Thou shad'st The full blaze of thy beams. --Milton.

   4. To pain in obscure colors; to darken.

   5. To mark with gradations of light or color.

   6. To present a shadow or image of; to shadow forth; to
      represent. [Obs.]

            [The goddess] in her person cunningly did shade That
            part of Justice which is Equity.      --Spenser.

Source : WordNet®

shading
     n 1: graded markings that indicate light or shaded areas in a
          drawing or painting
     2: a gradation involving small or imperceptible differences
        between grades [syn: {blending}]