- [Geom] A solid whose bases or ends are any similar, equal, and parallel plane figures, and whose sides are parallelograms.
- [Opt] 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.
- [Crystallog] A form the planes of which are parallel to the vertical axis. See Form (n.), 13.
Note: ☞ Prisms of different forms are often named from the figure of their bases; as, a triangular prism, a quadrangular prism, a rhombic prism, etc.
Etymology: L. prisma, Gr. pri`sma, fr. pri`zein pri`ein, to saw: cf. F. prisme