from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A solid figure whose bases or ends have the same size and shape and are parallel to one another, and each of whose sides is a parallelogram.
  • n. A transparent body of this form, often of glass and usually with triangular ends, used for separating white light passed through it into a spectrum or for reflecting beams of light.
  • n. A cut-glass object, such as a pendant of a chandelier.
  • n. A crystal form consisting of three or more similar faces parallel to a single axis.
  • n. A medium that misrepresents whatever is seen through it.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A polyhedron with parallel ends of the same size and shape, the other faces being parallelogram-shaped sides.
  • n. A transparent block in the shape of a prism (typically with triangular ends), used to split or reflect light.
  • n. A crystal in which the faces are parallel to the vertical axis.

from the GNU version of the Collaborative International Dictionary of English

  • n. A solid whose bases or ends are any similar, equal, and parallel plane figures, and whose sides are parallelograms.
  • n. 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.
  • n. A form the planes of which are parallel to the vertical axis. See Form, n., 13.

from The Century Dictionary and Cyclopedia

  • n. In geometry, a solid whose bases or ends are any similar, equal, and parallel plane polygons, and whose sides are parallelograms.
  • n. Specifically An optical instrument consisting of a transparent, medium so arranged that the surfaces which receive and transmit light form an angle with each other: usually of a triangular form with well-polished sides, which meet in three parallel lines, and made of glass, rock-salt, or quartz, or a liquid, as carbon disulphid, contained in a prismatic receptacle formed of plates of glass.
  • n. In crystallography, a form consisting of planes, usually four, six, eight, or twelve, which are parallel to the vertical axis.
  • n. In canals, a part of the water-space in a straight section of a canal, considered as a parallelepiped.
  • n. In weaving, same as pattern-box
  • n. A form of illuminator consisting of a prism with two convex surfaces, by which the light is brought to a focus upon the object.
  • n. According to some authors any form having two pairs of parallel faces is called a prism; in this sense the term includes the domes of the orthorhombic system (this name being then restricted to a form having two faces only intersecting in an edge) and the hemipyramids of the monoclinic system.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a polyhedron with two congruent and parallel faces (the bases) and whose lateral faces are parallelograms
  • n. optical device having a triangular shape and made of glass or quartz; used to deviate a beam or invert an image


Late Latin prīsma, from Greek prīsma, thing sawed off, prism, from prīzein, to saw, variant of prīein.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Late Latin prisma, from Ancient Greek πρίσμα (prisma, "something sawed"), from πρίζειν (prizein, "to saw"). (Wiktionary)



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