Polyhedron \Pol`y*he"dron\, n.; pl. E. {Polyhedrons}., L. {Polyhedra}. [NL., fr. Gr. ? with many seats or sides; poly`s many + ? a seat or side: cf. F. poly[`e]dre.] 1. (Geom.) A body or solid contained by many sides or planes. [1913 Webster] 2. (Opt.) A polyscope, or multiplying glass. [1913 Webster]