Not forming a syllable or the nucleus of a syllable; consisting of a consonant sound accompanied in the same syllable by a vowel sound or consisting of a vowel sound dominated by other vowel sounds in a syllable (as the second vowel in a falling diphthong):
— The nonsyllabic `n' in `botany' when it is pronounced `botny'.
— The nonsyllabic `i' in `oi'.

synoniem: unsyllabic.

of speech sounds Not forming or capable of forming the nucleus of a syllable.