The Collaborative International Dictionary of English v.0.48:

Silicate \Sil"i*cate\, n.[Cf. F. silicate.] (Chem.)
   A salt of silicic acid.
   [1913 Webster]

   Note: In mineralogical chemistry the silicates include; the
         unisilicates or orthosilicates, salts of orthosilicic
         acid; the bisilicates or metasilicates, salts of
         metasilicic acid; the polysilicates or acid silicates,
         salts of the polysilicic acids; the basic silicates or
         subsilicates, in which the equivalent of base is
         greater than would be required to neutralize the acid;
         and the hydrous silicates, including the zeolites and
         many hydrated decomposition products.
         [1913 Webster]

WordNet (r) 3.0 (2006):

silicate
    n 1: a salt or ester derived from silicic acid