radioactivity radioactively • radioamplifier · · · Info · Definitions · Synonyms · Characters · · radioactivity · · Text Latin · · Script 13 · · Length Definitions · · · (noun) the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay. Synonyms: radiation. · · Noun Definition 1 Synonyms · · · radiation · · Synonym 1 Characters · · a latin small letter a U+0061 c latin small letter c U+0063 d latin small letter d U+0064 i latin small letter i U+0069 o latin small letter o U+006F r latin small letter r U+0072 t latin small letter t U+0074 v latin small letter v U+0076 y latin small letter y U+0079