noun Physics.

  1. an atom of antimatter.


  1. an atom composed of antiparticles, in which the nucleus contains antiprotons with orbiting positrons

  1. An atom composed of antiparticles. An antiatom consists of positrons, antiprotons, and antineutrons. It has the same mass and spin as an ordinary atom, and the same amount of charge and magnetic moment, but the charge and magnetic moment are the opposite of those of an ordinary atom.
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