To Infiltrate

1. (transitive, intransitive) To surreptitiously penetrate, enter or gain access to.
2. (transitive, intransitive, of a liquid) To pass through something by filtration.
3. (transitive) To cause (a liquid) to pass through something by filtration.
4. (transitive, intransitive, medicine) To invade or penetrate a tissue or organ.
5. (transitive, military) To send (soldiers, spies etc.) through gaps in the enemy line.Antonym: exfiltrate
6. (intransitive, of an intravenous needle) To move from a vein, remaining in the body.