Source : Webster's Revised Unabridged Dictionary (1913)

Half tone \Half tone\, or Half-tone \Half"-tone`\, n.
   1. (Fine Arts)
      (a) An intermediate or middle tone in a painting,
          engraving, photograph, etc.; a middle tint, neither
          very dark nor very light.
      (b) A half-tone photo-engraving.

   2. (Music) A half step.