“+ noun
Etymology: semi- + vowel
1. : any speech sound not a stop, aspirate, or vowel, and not at any stage of the language having a stop as a component — used especially of ancient Greek
λ, μ, ν, γ nasal, ρ, and σ were semivowels
2. : one of the glides y, w, r
3. : a letter representing one of these sounds