Phonet. a voiced consonant that is less sonorous than a vowel but more sonorous than an unvoiced plosive and that may occur as a syllabic: English sonorants are (l), (r), (w), (y), (m), (n), and (ŋ)
Origin:
sonor(ous) + (conson)ant
See sonorant in American Heritage Dictionary 4
noun
A usually voiced speech sound characterized by relatively free air flow through the vocal tract and capable of being syllabic, as a vowel, liquid, or nasal.