scalenohedron

from The Century Dictionary.

• noun In crystallography, a twelve-sided form under the rhombohedral division of the hexagonal system, in which the faces are scalene triangles. It is regarded as a hemihedral form of the double twelve-sided pyramid. See hemihedral.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Crystallog.) A pyramidal form under the rhombohedral system, inclosed by twelve faces, each a scalene triangle.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A rhombohedral polyhedron having twelve sides, each in the form of a scalene triangle