Definition of pion in English:

pion

noun

Physics
  • A meson having a mass approximately 270 times that of an electron.

    Also called pi-meson
    • ‘Kaons and pions are examples of particles known as mesons, which contain a quark and an antiquark.’
    • ‘In turn, these decay into other subatomic particles, like kaons and pions.’
    • ‘The proton and the neutron are baryons; the electron, the muon, and the neutrino are leptons; whilst the pions are mesons.’
    • ‘A neutral pion consists of a down quark and a down antiquark.’
    • ‘He worked primarily on the interaction of pions with protons.’

Origin

1950s: from pi (the letter used as a symbol for the particle) + -on.

Pronunciation

pion

/ˈpʌɪɒn/