astatine astaticism • astatize · · · Info · Definitions · Synonyms · Characters · · astatine · · Text Latin · · Script 8 · · Length Definitions · · · (noun) a highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thorium. Synonyms: At, atomic number 85. · · Noun Definition 1 Synonyms · · · at · · Synonym 1 atomic number 85 · · Synonym 2 Characters · · a latin small letter a U+0061 e latin small letter e U+0065 i latin small letter i U+0069 n latin small letter n U+006E s latin small letter s U+0073 t latin small letter t U+0074