Pull off

A pull-off is a stringed instrument plucking technique performed by "pulling" the finger off a string off the fingerboard of either a fretted or unfretted instrument.

A pull-off is performed on a string which is already vibrating; when the fretting finger is pulled off (exposing the string either as open or as stopped by another fretting finger lower on the same string) the note playing on the string changes to the new, longer vibrating length of the string. Pull-offs are performed on both fretted instruments (e.g., electric guitar) and unfretted instruments (e.g., violin). They are used to sound grace notes with the transition from one note to the other sounding gentler and less percussive because the string is not picked or bowed again to produce the sound of the second note.

In the transition between the initial and final notes, the string may vibrate in an inharmonic manner for several cycles if it is plucked with the fretting finger, because the string is being plucked in a part of the string not usually used for plucking. The result, a slight "quack" sound, may be particularly audible when the interval of the pull-off is large. This transition also consumes some of the vibrational energy in the sounded string, with the effect that the second note is generally much quieter than the original.

On most acoustic instruments, this means the second note has little sustain. As a result, in acoustic music, pull-offs are primarily used as an embellishment. Performers of plucked instruments tend to use "pull-offs" when playing grace notes, usually in conjunction with multiple hammer-ons and strumming or picking to produce a rapid, rippling effect. In rock and heavy metal music, electric guitars are often performed with overdriven amplifiers and/or guitar effects such as distortion pedals and compression pedals are used, which add substantial sustain to the sound. With this type of electronic gear and a powerful instrument amplifier nearing the threshold of feedback, pull-offs can even be used to play sustained notes.

...
Wikipedia