Wordnet 3.0
ADJECTIVE (2)
1. 
 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); 
- Example: "the nonsyllabic `n' in `botany' when it is pronounced `botny'"- Example: "the nonsyllabic `i' in `oi'"[syn: nonsyllabic, unsyllabic]
2.  (of speech sounds) not forming or capable of forming the nucleus of a syllable; 
- Example: "initial 'l' in 'little' is nonsyllabic"
WordNet (r) 3.0 (2006):
nonsyllabic
    adj 1: 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'" [syn: nonsyllabic,
           unsyllabic] [ant: syllabic]
    2: (of speech sounds) not forming or capable of forming the
       nucleus of a syllable; "initial 'l' in 'little' is
       nonsyllabic" [ant: syllabic]