—v.t. 1. to filter into or through; permeate.
2. to cause to pass in by filtering.
3. to move into (an organization, country, territory, or the like) surreptitiously and gradually, esp. with hostile intent: The troops infiltrated the enemy lines. 4. 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.
—v.i. 1. to pass into or through a substance, place, etc., by or as by filtering.
2. Pathol.to penetrate tissue spaces or cells.
—n. 1. something that infiltrates.
2. Pathol.any substance penetrating tissues or cells and forming a morbid accumulation.