subatomic particle n.
Any of various units of matter below the size of an atom, including the elementary particles and hadrons.
| subatomic particle (sŭb'ə-tŏm'ĭk) Any of various particles of matter that are smaller than a hydrogen atom. Protons, neutrons, and electrons are subatomic particles, as are all hadrons and leptons. See also composite particle, elementary particle. |