| Tufa 1. (n.) A soft or porous stone formed by depositions from water, usually calcareous; -- called also calcareous tufa. 2. (n.) A friable volcanic rock or conglomerate, formed of consolidated cinders, or scoria. Thesaurus Entries aa, abyssal rock, bedrock, block lava, brash, breccia, conglomerate, crag, druid stone, festooned pahoehoe, gneiss, granite, igneous rock, lava, limestone, living rock, magma, mantlerock, metamorphic rock, monolith, pahoehoe, pillow lava, porphyry, pudding stone, regolith, rock, ropy lava, rubble, rubblestone, sandstone, sarsen, schist, scoria, scree, sedimentary rock, shelly pahoehoe, stone, talus, tufa, tuff |