Tunnel

1. (noun) An underground or underwater passage. 2. (noun) A passage through or under some obstacle. 3. (noun) A hole in the ground made by an animal, a burrow. 4. (noun) A wrapper for a protocol that cannot otherwise be used because it is unsupported, blocked, or insecure. 5. (noun) 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. 6. (noun) The opening of a chimney for the passage of smoke; a flue. 7. (noun) 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. 8. (verb) To make a tunnel through or under something; to burrow. 9. (verb) To dig a tunnel. 10. (verb) To transmit something through a tunnel (wrapper for insecure or unsupported protocol). 11. (verb) To insert a catheter into a vein to allow long-term use. 12. (verb) To undergo the quantum-mechanical phenomenon where a particle penetrates through a barrier that it classically cannot surmount.