Wiktionary
disphenoid
a. 1 (context mineralogy English) Describing a wedge-shaped crystal form of the tetragonal or orthorhombic system. 2 (context mineralogy English) Describing a crystal form bounded by eight scalene triangles arranged in pairs, constituting a tetragonal scalenohedron. n. (context geometry English) A polyhedron whose four faces are identical isosceles or scalene triangles.