Tunnels

noun

1. An underground or underwater passage.
2. A passage through or under some obstacle.
3. A hole in the ground made by an animal, a burrow.
4. A wrapper for a protocol that cannot otherwise be used because it is unsupported, blocked, or insecure.
5. 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.