/ Dictionary / Index D diffraction grating: Meaning and Definition of Find definitions for: diffrac'tion grat"ing Pronunciation: [key] — Physics. Physics. a band of equidistant, parallel lines, usually more than 5000 per inch (2000 per centimeter), ruled on a glass or polished metal surface for diffracting light to produce optical spectra. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. diffraction diffractive Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language