A <syllabic consonant> is a <consonant> functioning as a <syllable nucleus>. Consonant articulation and nuclear position describe different properties, so the combination is not contradictory. In phonetic transcription, a mark below the symbol can indicate syllabicity, as in `[n̩]`.<Essentials of Linguistics (2nd edition) by Catherine Anderson and others>[§3.10, syllabic consonants and syllable nuclei]{ref}

Some pronunciations of English “button” use a final syllabic `[n̩]`; others contain a <vowel> before the final nasal. The first pattern does not require an unrecorded vowel simply because the word has a second <syllable>. Listening and inspecting the acoustic interval can help distinguish the realizations, while identifying a syllable boundary is not equivalent to finding a silent gap in the waveform.


 Syllabic consonant (source code)