lepton2 Syllabification: (lep·ton)Pronunciation: /ˈlepˌtän/Definition of lepton noun Physics a subatomic particle, such as an electron, muon, or neutrino, that does not take part in the strong interaction. Derivatives leptonicPronunciation: /lepˈtänik/ adjective Origin: 1940s: from Greek leptos 'small' + -onlepton in other Oxford dictionaries Definition of lepton in the British & World English dictionary