Tu"fa (?), [It. fufo soft, sandy stone, L. tofus, tophus. Cf. Tofus, Toph, and Tophin.] Min. (a)
A soft or porous stone formed by depositions from water, usually calcareous; -- called also calcareous tufa.
(b)
A friable volcanic rock or conglomerate, formed of consolidated cinders, or scoria.
© Webster 1913.