[1] : The Collaborative International Dictionary of English v.0.48

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.
   1913 webster

   note: the dutch trass is made by burning and grinding a soft
         grayish rock found on the lower rhine.
         1913 webster
see also:
terrace tarras tarrace terras 

Trass >> T Words
Trass, definition of term: Trass
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