DICT.TW Dictionary Taiwan

 trass
 火山土

 Trass n.  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.]
 Note: ☞ The Dutch trass is made by burning and grinding a soft grayish rock found on the lower Rhine.
 ◄ ►