A Confined Aquifer is an Aquifer in which Ground Water is confined under pressure which is significantly greater than atmospheric pressure.
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A Confined Aquifer is an Aquifer bounded on the top by confining materials such as rock formations
Other /More definition:
A confined aquifer is soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.