to filter into or through; permeate.

to cause to pass in by filtering.

to move into (an organization, country, territory, or the like) surreptitiously and gradually, esp. with hostile intent

The troops infiltrated the enemy lines.

to pass a small number of (soldiers, spies, or the like) into a territory or organization clandestinely and with hostile or subversive intent

The intelligence agency infiltrated three spies into the neighboring country.

to pass into or through a substance, place, etc., by or as by filtering.

Pathology . to penetrate tissue spaces or cells.

something that infiltrates.

Pathology . any substance penetrating tissues or cells and forming a morbid accumulation.

verb

access , crack * , edge in , filter through , foist , impregnate , insinuate , penetrate , percolate * , permeate , pervade , saturate , sneak in , tinge , work into , worm into , edge , wind , work , worm , leak , seep