Permeability is a measure of the ease with which a material, such as soil or a rock, allows fluids or gases to pass through it. It is measured in terms of the rate of flow of a fluid or gas through a given thickness of the material. The higher the permeability, the easier it is for fluids or gases to pass through the material. Soil permeability is an important consideration in evaluating the potential for groundwater contamination, as it affects how easily contaminants can move through the soil.