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.