- Phonetics. a speech sound of vowel quality used as a consonant, as (w) in wet or (y) in yet.
- a vowel-like sound that acts like a consonant, in that it serves the same function in a syllable carrying the same amount of prominence as a consonant relative to a true vowel, the nucleus of the syllable. In English and many other languages the chief semivowels are (w) in well and (j), represented as y, in yell
- a frictionless continuant classified as one of the liquids; (l) or (r)