Vibrato is an expressive technique used by musicians where they slightly fluctuate the pitch of a sustained note to add warmth and richness to the sound.
Related terms
Tremolo: Rapidly repeating one note or alternating between two different pitches.
Portamento/Glide: Sliding smoothly from one pitch to another.
Glissando: Sliding rapidly through all the pitches within an interval or across multiple octaves.