frontal sinus frontally • frontal suture · · · Info · Definitions · Characters · · frontal sinus · · Text Common · · Latin · · Scripts 13 · · Length 4 · · Syllables Definitions · · · (noun) one of a pair of cavities in the frontal bone. Synonyms: frontal sinus. · · Noun Definition 1 Characters · · space U+0020 a latin small letter a U+0061 f latin small letter f U+0066 i latin small letter i U+0069 l latin small letter l U+006C 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 t latin small letter t U+0074 u latin small letter u U+0075