Tetrahedron

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Tetrahedron \Tet`ra*he"dron\, n. [Tetra- + Gr. ? seat, base, fr.
     ? to sit.] (Geom.)
     A solid figure inclosed or bounded by four triangles.
     [1913 Webster]
  
     Note: In crystallography, the regular tetrahedron is regarded


           as the hemihedral form of the regular octahedron.
           [1913 Webster]
  
     {Regular tetrahedron} (Geom.), a solid bounded by four equal
        equilateral triangles; one of the five regular solids.
        [1913 Webster]

From WordNet (r) 2.0 [wn]:

  tetrahedron
       n : any polyhedron having four plane faces
       [also: {tetrahedra} (pl)]