Bit Whirl (drilling) : The motion that a bit makes when it does not rotate about its center. This may manifest itself in out of round holes and severe bit damage. Generally a poor drilling performance
George E. King Engineering, 5000 Oilfield Terms: A Glossary of Petroleum Engineering Terms, Abbreviations and Acronyms, US 2010. http://gekengineering.com/Downloads/Free_Downloads /Glossary_of_Petroleum_Engineering_Terms_25_August _2010.pdf, (Oil - Amer) {593}