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[an-tee-pahr-ti-kuh l, an-tahy-] /ˈæn tiˌpɑr tɪ kəl, ˈæn taɪ-/
noun, Physics.
a particle all of whose properties, as mass, spin, or charge, have the same magnitude as but, where appropriate, the opposite sign of a specific elementary particle; neutral pions, photons, and gravitons are considered to be their own antiparticles:
The positron is the antiparticle of the electron.
Compare antimatter, annihilation (def 3).
Origin of antiparticle
1930-35; anti- + particle Unabridged
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Examples from the web for antiparticle
  • When one antiparticle is attracted over the event horizon and its matching particle escapes, radiation seems to be emitted.
  • Pair production is the production of a particle of matter and its antiparticle.
  • The question is whether the dark matter particles are particle-antiparticle pairs or not.
  • His equations predicted the existence of an antiparticle, which was later confirmed by experiment.
  • Energy is an intrinsic part of the vacuum, and manifests itself in particle-antiparticle pairs.
  • It is now believed that every fundamental particle has a corresponding antiparticle.
  • The high energy density produced quark-antiquark electron-positron, and other particle-antiparticle pairs.
  • Some particle-antiparticle pairs, however, are only distinguished by their signs.
  • One of the biggest questions is whether neutrinos are their own antiparticle.
  • Photons are their own antiparticle, but matter partners with antimatter, e g electron and positron or proton and antiproton.
British Dictionary definitions for antiparticle


any of a group of elementary particles that have the same mass and spin as their corresponding particle but have opposite values for all other nonzero quantum numbers. When a particle collides with its antiparticle, mutual annihilation occurs
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
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antiparticle in Science
  (ān'tē-pär'tĭ-kəl, ān'tī-)   
A subatomic particle, such as an antiproton, having the same mass as its corresponding particle, but opposite values of other properties such as charge, parity, spin, and direction of magnetic moment. For example, the antiparticle of the electron is the positron, which has a charge that is equal in magnitude to that of the electron but opposite in sign. Some particles, such as photons, are nondistinct from their antiparticles. When a particle and its antiparticle collide, they may annihilate one other and produce other particles.
The American Heritage® Science Dictionary
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antiparticle in Culture

antiparticle definition

In physics, a rare form of subatomic matter that is a mirror image of normal matter. The antiparticle corresponding to an elementary particle has the same mass as the particle but is opposite in all other properties. The antiparticle corresponding to an electron is a positron, which has the same mass as an electron but a positive charge. Antiprotons have the same mass as protons but a negative charge. When matter and antimatter come together, the two particles annihilate each other, converting their mass into energy or into other types of particles.

Note: As far as scientists can tell, there is almost no naturally occurring antimatter in the universe, although it is possible to make antimatter in particle accelerators.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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