Artificial Harmonic

From GuitarWiki

A Harmonic performed by placing your left finger on a fret and, with a flatpick, plucking the fretted string with your right hand. Immediately afterwards, your right-hand thumb briefly touches the string in a certain area. This produces a harmonic on that string, which can be bent with a left-hand finger to create a vibrato effect. This technique is used heavily in modern Heavy Metal music, and fairly often in Rock genres.

See also Pinched Harmonic.