Tarrace \Tar"race\, n.
   See Trass. [Obs.]
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Trass \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.]
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   Note: The Dutch trass is made by burning and grinding a soft
         grayish rock found on the lower Rhine.
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