amnion amniomancy • amnionate · · · Info · Definitions · Synonyms · Characters · · amnion · · Text Latin · · Script 6 · · Length 2 · · Syllables Definitions · · · (noun) thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals). Synonyms: amniotic sac, amnios. · · Noun Definition 1 Synonyms · · · amniotic sac · · Synonym 1 amnios · · Synonym 2 Characters · · a latin small letter a U+0061 i latin small letter i U+0069 m latin small letter m U+006D n latin small letter n U+006E o latin small letter o U+006F