Tū'fȧ or Tu'fȧ, n.

n. [It. tufo, soft, sandy stone, Fr. tuf, Ger. tuff, tuf, tof, Lat. 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 volcanic sand-rock, rather friable, formed of agglutinated, volcanic earth or scoria; also, a similar rock of trap or basaltic material. Dana.