(noun) finely pulverized gypsum used especially as a pigment.
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Noun Definition 1
(noun) fine white clay used in making tobacco pipes and pottery and in whitening leather. Synonyms: pipeclay.
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Noun Definition 2
(noun) 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). Synonyms: china clay, china stone, kaolin, kaoline, porcelain clay.