hydrogen hydrogel • hydrogenase · · · Info · Definitions · Synonyms · Characters · · hydrogen · · Text Latin · · Script 8 · · Length Definitions · · · (noun) a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe. Synonyms: H, atomic number 1. · · Noun Definition 1 Synonyms · · · h · · Synonym 1 atomic number 1 · · Synonym 2 Characters · · d latin small letter d U+0064 e latin small letter e U+0065 g latin small letter g U+0067 h latin small letter h U+0068 n latin small letter n U+006E o latin small letter o U+006F r latin small letter r U+0072 y latin small letter y U+0079