1. n. [Drilling]

The tool used to crush or cut rock. Everything on a drilling rig directly or indirectly assists the bit in crushing or cutting the rock. The bit is on the bottom of the drillstring and must be changed when it becomes excessively dull or stops making progress. Most bits work by scraping or crushing the rock, or both, usually as part of a rotational motion. Some bits, known as hammer bits, pound the rock vertically in much the same fashion as a construction site air hammer.

See related terms: antiwhirl bit,  bit breaker,  bottomhole assembly,  drill collar,  jet,  make hole,  polycrystalline diamond compact bit,  roller cone bit