meerschaum

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A fine, compact, usually white claylike mineral of hydrous magnesium silicate, H₄Mg₂Si₃O₁₀, found in the Mediterranean area and used in fashioning tobacco pipes and as a building stone. Also called sepiolite.
2. n. A tobacco pipe with a bowl made of this mineral.

Century Dictionary and Cyclopedia

1. n. A hydrated silicate of magnesium, occurring in fine white clay-like masses, which when dry will float on water; sepiolite. The name, from the German for ‘sea-foam,’ alludes to the lightness and the snow-white color. It is found in various regions, but occurs chiefly in Asia Minor, Livadia, and the island of Eubœa. When first taken out it is soft, and makes lather like soap. It is manufactured into tobacco-pipes, which, after being carved or turned, are baked to dry them, then boiled in milk, polished, and finally boiled in oil or wax. Artificial meerschaum is made from the chips and waste left from meerschaum-cutting, consolidated by pressure. Meerschaum is imitated also in plaster of Paris, treated with paraffin and colored with gamboge and dragon's-blood, and in other ways.
2. n. A pipe made from this substance. Such pipes are valued from their taking a rich brown color from the oil of tobacco gradually absorbed by the material.

Wiktionary

1. n. uncountable A soft white mineral, chiefly used for smoking-pipes and cigar holders.
2. n. countable A smoking-pipe made from meerschaum.

GNU Webster's 1913

1. n. (Min.) A fine white claylike mineral, soft, and light enough when in dry masses to float in water. It is a hydrous silicate of magnesia, and is obtained chiefly in Asia Minor. It is manufacturd into tobacco pipes, cigar holders, etc. Also called sepiolite.
2. n. A tobacco pipe made of this mineral; a meerschaum pipe.

WordNet 3.0

1. n. a pipe having a bowl made of meerschaum
2. n. a white clayey mineral