Penetrated or secretly entered by someone or something.
The organization was infiltrated by spies who gathered sensitive information.
Permeated or spread through with a substance, especially an abnormal one in medical contexts.
The infiltrated lung tissue appeared opaque on the X-ray.
infiltrateverb
To enter or gain access to an organization, place, or system surreptitiously and gradually, especially in order to acquire secret information or cause damage.
The spy managed to infiltrate the enemy's headquarters without being detected.
To permeate or become a part of something gradually, often in a way that is not immediately noticeable.
Over time, new ideas began to infiltrate the traditional culture of the community.