tunnel

An underground or underwater passage.

A passage through or under some obstacle.

A hole in the ground made by an animal, a burrow.

A wrapper for a protocol that cannot otherwise be used because it is unsupported, blocked, or insecure.

A vessel with a broad mouth at one end, a pipe or tube at the other, for conveying liquor, fluids, etc., into casks, bottles, or other vessels; a funnel.

The opening of a chimney for the passage of smoke; a flue.

A level passage driven across the measures, or at right angles to veins which it is desired to reach; distinguished from the drift, or gangway, which is led along the vein when reached by the tunnel.

To make a tunnel through or under something; to burrow.

To dig a tunnel.

To transmit something through a tunnel (wrapper for insecure or unsupported protocol).

To insert a catheter into a vein to allow long-term use.

To undergo the quantum-mechanical phenomenon where a particle penetrates through a barrier that it classically cannot surmount.