n. (pl. octahedrons or octahedra) 1 a solid figure contained by eight (esp. triangular) plane faces. 2 a body, esp. a crystal, in the form of a regular octahedron. regular octahedron an octahedron contained by equal and equilateral triangles. octahedral adj.
[ Gk oktaedron (as OCTA-, -HEDRON) ]