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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 ]