Definition of: prism

(priz′əm) noun
1. Geom. A solid whose bases or ends are any similar equal and parallel plane figures, and whose lateral faces are parallelograms.
2. Optics An instrument consisting of such a solid, usually having triangular ends and made of glass or other translucent substance, its refracting surfaces making an angle with each other.
3. Any medium that resolves a seemingly simple matter into its elements.
4. The spectrum.
5. Mineral. A crystal form consisting of three or more intersecting planes whose intersections are parallel and vertical.
—Nicol prism A prism of calcite (Iceland spar) so cut that light emerging from it is polarized in a definite plane: used in polarizing microscopes, etc. [<LL prisma <Gk., something sawed <prixein saw]
PRISM