/ Dictionary / Index E elementary particle: Meaning and Definition of Find definitions for: el'emen'tary par'ticle Pronunciation: [key] — Physics. Physics. any lepton, hadron, photon, or graviton, the particles once thought to be the indivisible components of all matter or radiation. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. elementary function elementary process Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language