Infiltration refers to the process by which water or other substances penetrate into the soil or a material. In environmental science, it is crucial for understanding how groundwater is replenished and how pollutants can spread through soil. The rate of infiltration can be affected by factors such as soil type, vegetation, and land use. In a different context, infiltration can also describe the act of secretly entering a group or organization to gather information or influence its activities. This tactic is often used in espionage or intelligence operations, where agents may pose as members of a group to achieve their objectives.