infiltrate

(ĭn-fĭlˈtrātˌ, ĭnˈfĭl-)

1. a. To pass (troops, for example) surreptitiously into enemy-held territory.
   b. To penetrate with hostile intent: infiltrate enemy lines; terrorists that had infiltrated the country.
2. To enter or take up positions in gradually or surreptitiously, as for purposes of espionage or takeover: infiltrated key government agencies with spies.
3. To cause (a liquid, for example) to permeate a substance by passing through its interstices or pores.
4. To permeate (a porous substance) with a liquid or gas.

Related Forms:

• in·filˈtra·tive (-trə-tĭv) adjective

• in·filˈtra·tor noun