When infiltration happens in an ecosystem, it means water soaks down into the soil. When infiltration happens in a spy movie, it means that someone sneaks into a place to learn secret information.

Military or security infiltration happens when troops penetrate their enemy's front lines to attack more vulnerable areas, or when CIA agents go undercover, posing as members of a group in order to gather information. In science, infiltration generally refers to rainwater being absorbed by the ground, or groundwater entering sewers and causing overflows that harm the environment.

Definitions of infiltration

n a process in which individuals (or small groups) penetrate an area (especially the military penetration of enemy positions without detection)

Type of:
incursion, penetration
an attack that penetrates into enemy territory

n the slow passage of a liquid through a filtering medium

“the infiltration of seawater through the lava”
Type of:
the process whereby fluids pass through a filter or a filtering medium

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