Entry 1 sense Webster, 1913 Icositetrahedron · I·co·si·tet·ra·he·dron · IPA 01 n. A twenty-four-sided solid; a tetragonal trisoctahedron or trapezohedron. 1. A twenty-four-sided solid; a tetragonal trisoctahedron or trapezohedron.(Crystallog.)