3. vb. [Drilling]
To drill soft, unconsolidated, usually shallow formations by eroding the "rock" below the bit by hydraulic impact loading alone. Though not as common as in the past, a bit may be fitted with asymmetric nozzles, one large and two or more small nozzles. If drillstring rotation is prevented during this jetting operation, the different nozzles tend to cause greater erosion on one side than the other, allowing the well to be intentionally deviated.