neptunium neptunist • Nereid · · · Info · Definitions · Synonyms · Characters · · neptunium · · Text Latin · · Script 9 · · Length Definitions · · · (noun) a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium. Synonyms: Np, atomic number 93. · · Noun Definition 1 Synonyms · · · np · · Synonym 1 atomic number 93 · · Synonym 2 Characters · · e latin small letter e U+0065 i latin small letter i U+0069 m latin small letter m U+006D n latin small letter n U+006E p latin small letter p U+0070 t latin small letter t U+0074 u latin small letter u U+0075