Trāss, n.

n. [Written also tarrass, tarrace, terras.] [Ger. trass, tarrass, trassel, probably allied to Fr. terrasse, earth-work, from terre, Lat. terra, earth. Cf. TRASS.] (Min.) A volcanic earth or sand-rock resembling puzzolana, used as a cement; or a coarse sort of plaster or mortar, durable in water, and used to line cisterns and other reservoirs of water.

☞— The Dutch trass is made of a soft rock-stone, found near Collen, on the lower part of the Rhine. It is burned like lime, and reduced to powder in mills. It is of a grayish color.