Definitions
1.verbTo surreptitiously penetrate, enter or gain access to.
2.verb(of a liquid) To pass through something by filtration.
3.verbTo cause (a liquid) to pass through something by filtration.
4.verbTo invade or penetrate a tissue or organ."High-grade tumors often infiltrate surrounding structures."
5.verbTo send (soldiers, spies etc.) through gaps in the enemy line.
6.verb(of an intravenous needle) To move from a vein, remaining in the body.