radiothorium radiothermy • radiotoxemia · · · Info · Definitions · Synonyms · Characters · · radiothorium · · Text Latin · · Script 12 · · Length Definitions · · · (noun) radioactive isotope of thorium with mass number 228. Synonyms: thorium-228. · · Noun Definition 1 Synonyms · · · thorium-228 · · Synonym 1 Characters · · a latin small letter a U+0061 d latin small letter d U+0064 h latin small letter h U+0068 i latin small letter i U+0069 m latin small letter m U+006D o latin small letter o U+006F r latin small letter r U+0072 t latin small letter t U+0074 u latin small letter u U+0075