From Middle English infiltrate, from Medieval Latin infiltrātus, from infiltrō.

• (British) IPA: /ˈɪnfɪltɹeɪt/
• (America) IPA: /ˈɪnfəltɹeɪt/, /ɪnˈfɪltɹeɪt/

infiltrate (infiltrates, present participle infiltrating; simple past and past participle infiltrated)

1. (ambitransitive) To surreptitiously penetrate, enter or gain access to.

   The spy infiltrated the high-tech company and stole many secrets.

2. (transitive) To cause to penetrate in this way.

   The agency infiltrated several spies into the company.

3. (ambitransitive, of a liquid) To pass through something by filtration.
4. (transitive) To cause (a liquid) to pass through something by filtration.
5. (ambitransitive, medicine) To invade or penetrate a tissue or organ.

   High-grade tumors often infiltrate surrounding structures.

   In certain conditions, immune cells may infiltrate into the cerebrospinal fluid.

6. (transitive, military) To send (soldiers, spies etc.) through gaps in the enemy line.

   Antonyms: exfiltrate

7. (intransitive, of an intravenous needle) To move from a vein, remaining in the body.

• French: infiltrer
• German: infiltrieren
• Italian: infiltrare
• Russian: проса́чиваться
• Spanish: infiltrarse

• Italian: filtrare
• Spanish: infiltrar

• Italian: infiltrare
• Russian: проникать в тыл противника

infiltrate (plural infiltrates)

1. (pathology) Any undesirable substance or group of cells that has made its way into part of the body.
   • 2008, Jimmy D. Bartlett, Siret D. Jaanus, Clinical Ocular Pharmacology, page 539:

     One critical distinction to make is whether a focal corneal infiltrate is infected with bacteria or is a sterile immunologic response.

• German: Infiltrat