To move into (an object), such that one ends up inside it.
To become involved or interested in (a discussion, issue, or activity).
To enter (an unfavourable state).
To interrogate in order to arrive at a deeper understanding.
To put on (an item of clothing).
To cause to behave uncharacteristically; to possess.
To reach into or interact with (an object).
To surreptitiously penetrate, enter or gain access to.
To cause to penetrate in this way.
To invade or penetrate a tissue or organ.
To send (soldiers, spies, etc.) through gaps in the enemy line.
To pass through something by filtration.
To move from a vein, remaining in the body.
To cause (a liquid) to pass through something by filtration.
Any undesirable substance or group of cells that has made its way into part of the body.