sound barrier sound asleep • sound bite · · · Info · Definitions · Synonyms · Characters · · sound barrier · · Text Common · · Latin · · Scripts 13 · · Length 4 · · Syllables Definitions · · · (noun) the increase in aerodynamic drag as an airplane approaches the speed of sound. Synonyms: sonic barrier, sound barrier. · · Noun Definition 1 Synonyms · · · sonic barrier · · Synonym 1 Characters · · space U+0020 a latin small letter a U+0061 b latin small letter b U+0062 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 o latin small letter o U+006F r latin small letter r U+0072 s latin small letter s U+0073 u latin small letter u U+0075