icositetrahedron

from The Century Dictionary.

• noun In crystallography, a solid, belonging to the isometric system, which is contained by twenty-four similar four-sided planes; a tetragonal trisoctahedron, or trapezohedron.

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

• noun (Crystallog.) A twenty-four-sided solid; a tetragonal trisoctahedron or trapezohedron.

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

• noun mathematics Any of several solids having twenty-four faces.