The Collaborative International Dictionary of English v.0.48:

Frit \Frit\ (fr[i^]t), n. [F. fritte, fr. frit fried, p. p. of
   frire to fry. See Far, v. t.]
   1. (Glass Making) The material of which glass is made, after
      having been calcined or partly fused in a furnace, but
      before vitrification. It is a composition of silex and
      alkali, occasionally with other ingredients. --Ure.
      [1913 Webster]

   2. (Ceramics) The material for glaze of pottery.
      [1913 Webster]

   Frit brick, a lump of calcined glass materials, brought to
      a pasty condition in a reverberatory furnace, preliminary
      to the perfect vitrification in the melting pot.
      [1913 Webster]