antiparticle: Meaning and Definition of

an•ti•par•ti•cle

1. 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:Cf. antimatter, annihilation (def. 3). The positron is the antiparticle of the electron.