manganese manganeisen • manganesian · · · Info · Definitions · Synonyms · Characters · · manganese · · Text Latin · · Script 9 · · Length Definitions · · · (noun) a hard brittle grey polyvalent metallic element that resembles iron but is not magnetic; used in making steel; occurs in many minerals. Synonyms: Mn, atomic number 25. · · Noun Definition 1 Synonyms · · · mn · · Synonym 1 atomic number 25 · · Synonym 2 Characters · · 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 s latin small letter s U+0073