actinide actinic ray • actinide series · · · Info · Definitions · Synonyms · Characters · · actinide · · Text Latin · · Script 8 · · Length 3 · · Syllables Definitions · · · (noun) any of a series of radioactive elements with atomic numbers 89 through 103. Synonyms: actinoid, actinon. · · Noun Definition 1 Synonyms · · · actinoid · · Synonym 1 actinon · · Synonym 2 Characters · · a latin small letter a U+0061 c latin small letter c U+0063 d latin small letter d U+0064 e latin small letter e U+0065 i latin small letter i U+0069 n latin small letter n U+006E t latin small letter t U+0074