| Noun | 1. | optical prism - optical device having a triangular shape and made of glass or quartz; used to deviate a beam or invert an imagebiprism - an optical device for obtaining interference fringes erecting prism - a right-angled optical prism used to turn an inverted image upright optical device - a device for producing or controlling light prism spectroscope, spectroscope - an optical instrument for spectrographic analysis |