mass energy Massena quail • mass-energy equation · · · Info · Definitions · Characters · · mass energy · · Text Common · · Latin · · Scripts 11 · · Length 4 · · Syllables Definitions · · · (noun) (physics) the mass of a body regarded relativistically as energy. Synonyms: mass energy. · · Noun Definition 1 Characters · · space U+0020 a latin small letter a U+0061 e latin small letter e U+0065 g latin small letter g U+0067 m latin small letter m U+006D n latin small letter n U+006E r latin small letter r U+0072 s latin small letter s U+0073 y latin small letter y U+0079