nonsyllabic

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'”

(of speech sounds) not forming or capable of forming the nucleus of a syllable.

“initial `l' in `little' is nonsyllabic”