noun
: a boring system by which material loosened by a bit is borne to the surface in the annular space between the bit and casing by water forced down through the pipe bearing the bit
noun
: a boring system by which material loosened by a bit is borne to the surface in the annular space between the bit and casing by water forced down through the pipe bearing the bit
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012