Source : Webster's Revised Unabridged Dictionary (1913)

Ground \Ground\,
   imp. & p. p. of {Grind}.

   {Ground cock}, a cock, the plug of which is ground into its
      seat, as distinguished from a compression cock. --Knight.

   {Ground glass}, glass the transparency of which has been
      destroyed by having its surface roughened by grinding.

   {Ground joint}, a close joint made by grinding together two
      pieces, as of metal with emery and oil, or of glass with
      fine sand and water.

Source : WordNet®

ground glass
     n 1: glass that diffuses light due to a rough surface produced by
          abrasion or etching
     2: particulate glass made by grinding and used as an abrasive