The New Dictionary of Cultural Literacy, Third Edition. 2002.
prism
(PRIZ-uhm) A solid figure in geometry with bases or ends of the same size and shape and sides that have parallel edges. Also, an object that has this shape.
A prism of glass (or a similar transparent material) can be used to bend different wavelengths of light by different amounts through refraction. This bending separates a beam of white light into a spectrum of colored light.