pinch harmonics
On the guitar, pinch harmonics is the act of lightly touching a string with the edge of your thumb/palm (picking hand) after plucking it. Similar to natural harmonics except you're not playing off a fret. If you use a lot of distortion and gain it produces a squealing effect.
A lot of guitarists use pinch harmonics, most notably Zakk Wylde, but also players like ZZ Top, Dimebag Darrell, and even Steve Vai.
pinch harmonics by bryan18 August 21, 2005