elementary particle: Meaning and Definition of

el'emen'tary par'ticle

Pronunciation: [key]
— Physics. Physics.
  1. 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.