1. 
   trass
   <geology> 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...
   Found op http://www.mondofacto.com/facts/dictionary?trass
   
   
2. 
   Trass
   • (n.) 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.
   Found op http://thinkexist.com/dictionary/meaning/trass/
   
   
3. 
   Trass
   Trass is the local name of a volcanic tuff occurring in the Eifel, where it is worked for hydraulic mortar. It is a grey or cream-coloured fragmental rock, largely composed of pumiceous dust, and may be regarded as a trachytic tuff. It much resembles the Italian pozzolana and is applied to like pur...
   Found op http://en.wikipedia.org/wiki/Trass
   
   
4. 
   Trass
   Trass is a white to grey coloured volcanic tufa, formed of decomposed trachytic cinders, sometimes used as a cement.
   Found op http://www.probertencyclopaedia.com/browse/HT.HTM
   
   
5. 
   trass
   1) Volcanic earth
   Found op http://www.mijnwoordenboek.nl/EN/crossword-dictionary/trass/1
   
   

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