Infiltrate
Infiltrate , intransitive verb
[Prefix in- + filtrate: compare F, s'infiltrer. Compare Infilter.]
1.
To enter by penetrating the pores or interstices of a substance; to filter into or through something.
The water infiltrates through the porous rock.
2.
To enter secretly (into an organization, territory, etc.) for hostile purposes, such as spying or sabotage; as, the FBI infiltrated into the U. S. communist party's upper echelons; also used transitively; as, to infiltrate the opponent's organization; to infiltrate one's agents into a hostile country.
Infiltrate , transitive verb
To penetrate gradually; -- sometimes used reflexively. — J. S. Mill