(Latin: in-, "in" + filtratus, "felt")

infiltrate (s) (noun), infiltrates (pl)
1. A way to approach a structure or area in order to obtain secret information. A competing company has obtained the results of the profits for the year of another commercial business.
2. A number of cells in the body that have been affected by a disease: A chest radiograph revealed patchy infiltrates in Michael's lungs.
infiltrate (verb), infiltrates; infiltrated; infiltrating
1. To enter or to gain access to an organization, place, etc. secretly and gradually; especially in order to acquire secret information or to do harm: The criminal organization was infiltrated by undercover agents of the FBl.

The government infiltrated key enemy agencies with spies.

Some cybercriminals are infiltrating the contents of Internet sites in order to collect system profile data so the bad guys need to find ways to reach prospective victims and collect information about them in order to make sure targeted attacks are successful.

2. To accumulate substances or cells within a tissue that are either not normally found it it or are usually present only in smaller amounts: A drug; such as, a local anesthetic that has been into a tissue.

Excessive alcohol consumption can infiltrate the body and cause fat in the liver.

Radiologists use infiltrated to refer to the presence of a tumor or pneumonia in a tissue; such as, lung cancer as seen in a chest X-ray.

infiltration (s) (noun), infiltrations (pl)
1. Diffuse pulmonary infiltration is the accumulation of abnormal material in the lungs.
2. Fatty infiltration is the permeation of oily or greasy substance in cells or tissues.
3. Urinous infiltration is an introduction of urine resulting from a break in the continuity of the wall of the ureter or bladder which may be caused by cancer, trauma, or inflammation.
4. Military procedures against enemy forces: New tactics of infiltration were carried out by secretly trained troops that created demoralization of enemy soldiers as far as the command and the communication centers.
infiltrative (adjective), more infiltrative, most infiltrative
1. Descriptive of a substance that accumulates gradually into bodily tissues.
2. Pertaining to penetrating or slipping into an enemy line at weak or unguarded places.
infiltrative disorder (s) (noun), infiltrative disorders (pl)
An infiltrative disorder is a condition caused by the diffusion or accumulation in cells or tissues of substances not normally found in them; as in a disease that causes infection, inflammation, or the presence of a foreign substance.
infiltrator (s) (noun), infiltrators (pl)
Someone who gets into an organization or territory as an undercover or covert agent for the purpose of espionage: The commander of the military troops found out that his unit was infiltrated with enemy agents who were reporting his group's activities, movements, and plans to their own headquarters.