Particle Physics any of a class of subatomic particles that obey the Pauli exclusion principle and have fractional spin, including the leptons, quarks, and baryons
See fermion in American Heritage Dictionary 4
(fûrˈmē-ŏnˌ, fĕrˈ-)
noun
A particle, such as an electron, proton, or neutron, having half-integral spin and obeying statistical rules requiring that not more than one in a set of identical particles may occupy a particular quantum state.