The Collaborative International Dictionary of English v.0.48:

Metasilicic \Met`a*si*lic"ic\, a. [Pref. meta- + silicic.]
   (Chem.)
   Designating an acid derived from silicic acid by the removal
   of water; of or pertaining to such an acid.
   [1913 Webster]

   Note: The salts of metasilicic acid are often called
         bisilicates, in mineralogy, as Wollastonite (CaSiO3).
         [1913 Webster]

   Metasilicic acid (Chem.), a gelatinous substance, or white
      amorphous powder, analogous to carbonic acid, and forming
      many stable salts.
      [1913 Webster]