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)
source: WordNet 3.0
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.