infiltrate

To pass (troops, for example) surreptitiously into enemy-held territory.

To penetrate with hostile intent.

To enter or take up positions in gradually or surreptitiously, as for purposes of espionage or takeover.

To cause (a liquid, for example) to permeate a substance by passing through its interstices or pores.

To permeate (a porous substance) with a liquid or gas.

To gain entrance gradually or surreptitiously.

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

To pass by filtration; percolate through pores or interstices.

To pass into or through the pores or interstices of; filter into or through.