nonsyllabic has 1 distinct synonym spread across 1 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is syllabic.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
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'”
(of speech sounds) not forming or capable of forming the nucleus of a syllable
“initial `l' in `little' is nonsyllabic”
Synonyms, antonyms and the broader and narrower relations for nonsyllabic come from Princeton University’s WordNet. Full sources and licences.