fretless guitar
A fretless guitar is a guitar with a fingerboard without frets, typically a standard instrument that has had the frets removed, though some custom-built and commercial fretless guitars are occasionally made. Fretless bass guitars are readily available, with most major guitar manufacturers producing fretless models. The forerunner to fretless guitars like the Hawaiian Guitar is the traditional 3000 year old Indian Chitravina, aka Gotuvadyam, popularised globally by Chitravina N Ravikiran.
On the fretless guitar, the performer's fingers press the string directly against the fingerboard, as with a violin, resulting in a vibrating string that extends from the bridge (where the strings are attached) to the fingertip instead of to a fret.
This tag implicates guitar (learn more).