a. [ See Tetrahedron. ] 1. Having, or composed of, four sides. [ 1913 Webster ]
2. (Crystallog.) (a) Having the form of the regular tetrahedron. (b) Pertaining or related to a tetrahedron, or to the system of hemihedral forms to which the tetrahedron belongs. [ 1913 Webster ]
Tetrahedral angle (Geom.), a solid angle bounded or inclosed by four plane angles. [ 1913 Webster ]