Meson

[mee-zon, ‐son, mez-on, mes‐] /ˈmi zɒn, ‐sɒn, ˈmɛz ɒn, ˈmɛs‐/

noun
1.
Physics. any hadron, or strongly interacting particle, other than a baryon. Mesons are bosons, having spins of 0, 1, 2, …, and, unlike baryons, do not obey a conservation law.
/ˈmiːzɒn/
noun
1.
any of a group of elementary particles, such as a pion or kaon, that usually has a rest mass between those of an electron and a proton, and an integral spin. They are responsible for the force between nucleons in the atomic nucleus Former name mesotron See also muon
n.

subatomic particle, 1939, from Greek mesos “middle” (see medial (adj.)) + subatomic particle suffix -on. Earlier mesotron (1938). So called for being intermediate in mass between protons and electrons.
meson
(měz’ŏn’, měs’-, mē’zŏn’, -sŏn’)
Any of a family of subatomic particles that are composed of a quark and an antiquark. Their masses are generally intermediate between leptons and baryons, and they can have positive, negative, or neutral charge. Mesons form a subclass of hadrons and include the kaon, pion and J/psi particles. Mesons were originally believed to be the particles that mediated the strong nuclear force, but it has since been shown that the gluon mediates this force. See Table at subatomic particle.
meson [(mez-on, may-zon)]

An elementary particle in the atomic nucleus.