/ Dictionary / Index P prism diopter: Meaning and Definition of Find definitions for: prism' diop'ter Pronunciation: [key] — Optics. Optics. a unit of prismatic deviation, in which the number one represents a prism that deflects a beam of light a distance of one centimeter on a plane placed normal to the initial direction of the beam and one meter away from the prism. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. prism binocular prismoid Related Content Daily Word Quiz: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language