Definition of nucleonium in English:

nucleonium

noun

Particle Physics
rare
  • A particle consisting of a nucleon and the corresponding antinucleon bound to each other. Usually without article, and attributive.

Origin

1950s; earliest use found in The Physical Review. From nucle- + -onium.

Pronunciation

nucleonium

/njuːklɪˈəʊnɪəm/