A sound which has been slightly distorted by means of analog tape saturation or tube distortion, yielding a warm, full sound. Also, a sound which is spatially diffuse, accomplished by panning a signal hard left in the stereo spectrum, then delaying the signal slightly and panning the delayed signal hard right.
FAT
Meaning of FAT in English
Guitar English glossary. Английский словарь гитарных терминов . 2012