luminal Luminal • luminance · · · Info · Definitions · Synonyms · Characters · · luminal · · Text Latin · · Script 7 · · Length Definitions · · · (noun) a long-acting barbiturate used as a sedative. Synonyms: sodium thiopental, phenobarbital, phenobarbitone, Luminal, purple heart. · · Noun Definition 1 Synonyms · · · sodium thiopental · · Synonym 1 phenobarbital · · Synonym 2 phenobarbitone · · Synonym 3 purple heart · · Synonym 4 Characters · · a latin small letter a U+0061 i latin small letter i U+0069 l latin small letter l U+006C m latin small letter m U+006D n latin small letter n U+006E u latin small letter u U+0075