TRASS

trass. Trass, n. a gray or yellowish porous stone

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Trass (?), n. [[D. tras or Gr. trass, probably fr. It. terrazzo terrace. See Terrace.]] (Geol.) A white to gray volcanic tufa, formed of decomposed trachytic cinders; — sometimes used as a cement. Hence, a coarse sort of plaster or mortar, durable in water, and used to line cisterns and other reservoirs of water. [Formerly written also tarras, tarrace, terras.] ☞ The Dutch trass is made by burning and grinding a soft grayish rock found on the lower Rhine.