An Aquifer is an underground geological formation, or group of formations, containing water. They are sources of groundwater for wells and springs.

Other definition:
An aquifer is underground source of water.

Other definition:
An Aquifer is any underground geological formation containing water.

Other definition:
An Aquifer is a natural underground layer, often of sand or gravel, that contains water.

Other definition:
An Aquifer is Underground layer of rock or sand that stores water. Humans use wells to get drinking water from Aquifer

Other definition:

An Aquifer is an underground rock formation composed of sand, soil, gravel, or porous rock that can store and supply groundwater to wells and springs

Other definition:
An aquifer is a geologic formation(s) that is water bearing. A geological formation or structure that stores and/or transmits water, such as to Wells and springs. Use of the term is usually restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people's uses.

Other definition:
Aquifer is the porous, water-saturated layers of sand, gravel, or bedrock that can yield an economically significant amount of water.

Other definition:

an Aquifer is an underground reservoir-like layer of water. Most of the water in aquifers is contained in beds of sand, gravel, or other material and can be pumped to the surface.