A vertical installation in the ground to abstract groundwater. It is drilled (or bored) and lined with metal or plastic tubes to keep it open, and to protect against surface pollution. At depth, the tubes are slotted or filtered to allow water to enter but to prevent ingress of silt, sand or rock particles. In hard consolidated rock, the bore and intake sections may be unlined.
Borehole diameter is typically 10 to 30 cm, and depths range from a few metres to 100s of metres, with most less than 100 m. Colloquially, they are often called a well or water well. In South Asia, they are called tubewell.
Water is usually abstracted with an electrical submersible pump installed some metres below the water level with a pipe connection to the surface. Some boreholes are artesian, whereby they flow without pumping due to the groundwater pressure.
Some boreholes are installed only to measure groundwater levels or sample for water quality. These are called observation wells.
Designing and constructing a borehole is a highly specialist skill.