The Collaborative International Dictionary of English v.0.48:

Kaolin \Ka"o*lin\, Kaoline \Ka"o*line\, n. [Chin. kao-ling.]
   (Min.)
   A very pure white clay, ordinarily in the form of an
   impalpable powder, and used to form the paste of porcelain;
   China clay; porcelain clay. It is chiefly derived from the
   decomposition of common feldspar.
   [1913 Webster]

   Note: The name is now applied to all porcelain clays which
         endure the fire without discoloration.
         [1913 Webster]

WordNet (r) 3.0 (2006):

kaoline
    n 1: a fine usually white clay formed by the weathering of
         aluminous minerals (as feldspar); used in ceramics and as
         an absorbent and as a filler (e.g., in paper) [syn: china
         clay, china stone, kaolin, kaoline, porcelain
         clay, terra alba]