Infiltration

Noun

1. The act or process of infiltrating, as of water into a porous substance, or of a fluid into the cells of an organ or part of the body. process by which water on the ground surface enters the soil.
2. process by which water on the ground surface enters the soil.
3. The substance which has entered the pores or cavities of a body.
4. The act of secretly entering a physical location and/or organization.