/nooh tree"noh, nyooh-/ , n. , pl. neutrinos . Physics.
any of the massless or nearly massless electrically neutral leptons. There is a distinct kind of neutrino associated with each of the massive leptons. Cf. antineutrino, lepton, conservation of lepton number .
[ neutr ( o ) NEUTER, neutral + -ino -INE 2 ; coined by E. Fermi ]