infiltration >> ɪnfɪlˈtreɪʃ(ə)n
Definition: [noun] the action of entering or gaining access to an organization or place surreptitiously, especially in order to acquire secret information or cause damage.
Example: the army fenced parts of the border in an effort to stop militant infiltration
Definition: [noun] permeation of a liquid into something by filtration.
Example: improved water infiltration into the soil
Definition: [noun] the process of gradually permeating or becoming a part of something.
Example: the gradual infiltration of Boyce's music into the national consciousness