infiltrator

in·fil·trate  (n-fltrt, nfl-)

v. in·fil·trat·ed, in·fil·trat·ing, in·fil·trates

v.tr.

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.

v.intr.

To gain entrance gradually or surreptitiously.

n.

One that infiltrates, especially an abnormal substance that accumulates gradually in cells or body tissues.

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in·filtra·tive (-tr-tv) adj.

in·filtra·tor n.

Thesaurus

Noun	1.	infiltrator - someone who takes up a position surreptitiously for the purpose of espionage spy, undercover agent - (military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors
	2.	infiltrator - an intruder (as troops) with hostile intent interloper, intruder, trespasser - someone who intrudes on the privacy or property of another without permission