Prism

A solid whose bases or ends are any similar, equal, and parallel plane figures, and whose sides are parallelograms.

A transparent body, with usually three rectangular plane faces or sides, and two equal and parallel triangular ends or bases; -- used in experiments on refraction, dispersion, etc.

A form the planes of which are parallel to the vertical axis. See Form, n., 13.

optical device having a triangular shape and made of glass or quartz; used to deviate a beam or invert an image