Keyseat 3 : A condition wherein the borehole is abraded and extended sideways and with a diameter smaller than the drill collars and the bit; usually caused by the tool joints on the drill pipe. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}