Particle Physics a subatomic particle that is both a hadron and a fermion, as a nucleon or hyperon: the proton is the baryon with the smallest mass
See baryon in American Heritage Dictionary 4
(bărˈē-ŏnˌ)
noun
Any of a family of subatomic particles, including the nucleon and hyperon multiplets, that participate in strong interactions, are composed of three quarks, and are generally more massive than mesons. Also called heavy particle. See Table at subatomic particle.