The term for underground water under pressure that can rise above the ground level is called what?

The term referred to in the question describes a specific geological and hydrological phenomenon known as the artesian effect. This occurs in aquifers that are confined by impermeable rock or clay layers, allowing water within the aquifer to be pressurized. When a well is drilled into such a confined aquifer, the internal pressure can cause the water to rise above the level of the surrounding ground, often creating a natural fountain-like effect.

This process is distinct from other forms of water. For example, groundwater generally refers to all water located beneath the surface, without necessarily implying any pressure. Surface water pertains to water that collects on the surface, like lakes and rivers, and floodwater relates specifically to excess surface water, typically due to heavy rainfall or other unusual conditions. Each of these other terms describes different water contexts and does not encompass the specific characteristic of underground pressure that defines the artesian effect.