- an elementary particle having no charge and having a mass and spin equal to that of the but with magnetic moment opposite to that of the ; the antiparticle of the .
- Also an·ti-neu·tron. opposing the building, stockpiling, or use of The antineutron lobby was outnumbered. bombs:
- the antiparticle of a neutron; a particle having the same mass as the neutron but a magnetic moment of opposite sign
- The antiparticle that corresponds to the neutron.