protoactinium proto • protoalbumose · · · Info · Definitions · Synonyms · Characters · · protoactinium · · Text Latin · · Script 13 · · Length Definitions · · · (noun) a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead. Synonyms: protactinium, Pa, atomic number 91. · · Noun Definition 1 Synonyms · · · protactinium · · Synonym 1 pa · · Synonym 2 atomic number 91 · · Synonym 3 Characters · · a latin small letter a U+0061 c latin small letter c U+0063 i latin small letter i U+0069 m latin small letter m U+006D n latin small letter n U+006E o latin small letter o U+006F p latin small letter p U+0070 r latin small letter r U+0072 t latin small letter t U+0074 u latin small letter u U+0075