meson

me·son

noun \ˈmez-ˌän, ˈmēz-, ˈmēs-, ˈmes-\

Definition of MESON

: any of a group of unstable elementary particles that are subject to nuclear forces and have masses much greater than that of the electron

—me·son·ic \me-ˈzän-ik, mē-, -ˈsän-\ adjective