The Collaborative International Dictionary
Regular tetrahedron
Tetrahedron \Tet`ra*he"dron\, n. [Tetra- + Gr. ? seat, base, fr. ? to sit.] (Geom.) A solid figure inclosed or bounded by four triangles.
Note: In crystallography, the regular tetrahedron is regarded as the hemihedral form of the regular octahedron.
Regular tetrahedron (Geom.), a solid bounded by four equal equilateral triangles; one of the five regular solids.
WordNet
regular tetrahedron
n. a tetrahedron with four equilateral triangular faces
Usage examples of "regular tetrahedron".
The effect was as though one were looking down at the apex of a regular tetrahedron.
The Lunar system was the simplest, with just four entry points set at the vertices of a regular tetrahedron.