trisoctahedron

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A solid figure having 24 equal faces, every three of which correspond to one face of an octahedron.

from The Century Dictionary.

• noun In crystallography, a solid bounded by twenty-four equal faces, three corresponding to each face of an octahedron.
• noun This name is usually limited to the isometric form having triangular faces, formerly called a trigonal trisoctahedron.

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

• noun (Crystallog.) A solid of the isometric system bounded by twenty-four equal faces, three corresponding to each face of an octahedron.
• noun a trisoctahedron each face of which is a quadrilateral; called also trapezohedron and icositetrahedron.
• noun a trisoctahedron each face of which is an isosceles triangle.

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

• noun crystallography A solid of the isometric system bounded by 24 equal faces, three corresponding to each face of an octahedron.