Trass
Pronunciation : Trass
Part of Speech : n.
Etymology : [D. tras or Gr. trass, probably fr. It. terrazzo terrace. See Terrace.] (Geol.)
Definition : Defn: 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.]
Note: The Dutch trass is made by burning and grinding a soft grayish rock found on the lower Rhine.
Source : Webster's Unabridged Dictionary, 1913