infiltrate

Universal Words verb 1 ~ (sb) (into sth) to enter or make sb enter a place or an organization secretly, especially in order to get information that can be used against it: [VN] The headquarters had been infiltrated by enemy spies. * Rebel forces were infiltrated into the country. * [V] The CIA agents successfully infiltrated into the terrorist organizations. 2 ~ (into) sth (technical) (especially of liquids or gases) to pass slowly into sth: [V] Only a small amount of the rainwater actually infiltrates into the soil. [also VN] infiltration noun [U]: communist infiltration of the army * the infiltration of rain into the soil