Source : Webster's Revised Unabridged Dictionary (1913)

Isinglass \I"sin*glass\, n. [Prob. corrupted fr. D. huizenblas
   (akin to G. hausenblase), lit., bladder of the huso, or large
   sturgeon; huizen sturgeon + blas bladder. Cf. {Bladder},
   {Blast} a gust of wind.]
   1. A semitransparent, whitish, and very pure from of gelatin,
      chiefly prepared from the sounds or air bladders of
      various species of sturgeons (as the {Acipenser huso})
      found in the of Western Russia. It used for making
      jellies, as a clarifier, etc. Cheaper forms of gelatin are
      not unfrequently so called. Called also {fish glue}.

   2. (Min.) A popular name for mica, especially when in thin
      sheets.

Source : WordNet®

isinglass
     n : any of various minerals consisting of hydrous silicates of
         aluminum or potassium etc. that crystallize in forms that
         allow perfect cleavage into very thin leaves; used as
         dielectrics because of their resistance to electricity
         [syn: {mica}]