tunnel

noun

1. An underground or underwater passage.

   “In 1865 an outfit called the East London Railway Company bought the Brunel tunnel for £800,000, and in 1869 they opened a railway through it.”

2. A passage through or under some obstacle.

   “But very soon he grew to like it, for the Boy used to talk to him, and made nice tunnels for him under the bedclothes that he said were like the burrows the real rabbits lived in.”

   “Tunnels often feature in fictional journeys, so I will end with quotations from a fairly recent novel, Howard Spring's "Fame is the Spur", published in 1940, in which there is a journey from Manchester to Bradford via the Calder Valley route: "Ay, we're going through Todmorden. We'll soon be in t' tunnel, and when we get to t' other end we'll be in Yorkshire," and "Ah think this is t' filthiest tunnel in t' world."”

   “There are more than 1,500 railway tunnels in Britain and the majority are still in use, carrying working tracks beneath Britain's most inconvenient geographic features.”

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

   “And one great chimney, whose long tonnell thence, / The smoke forth threw”

7. 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. (figuratively)Anything that resembles a tunnel.

   “Especially in the Eden Valley, trees create what is almost a green tunnel (particularly in summer).”

verb

1. (transitive)To make a tunnel through or under something; to burrow.

   “The 1955 Act gave powers for compulsory acquisition of "easements", or permission to tunnel beneath dwelling houses instead of, as had previously been necessary, following approximately the course of surface roads.”

   “The 6.5km route is agreed from a junction with the relief lines of the Great Western main line to the west of Slough, the new link would tunnel under the M25 to reach Heathrow's Terminal 5 station, where space has been set aside to accommodate services from the west.”

2. (intransitive)To dig a tunnel.
3. To transmit something through a tunnel (wrapper for an insecure or unsupported protocol).
4. (transitive)To insert a catheter into a vein to allow long-term use.
5. To undergo the quantum-mechanical phenomenon where a particle penetrates through a barrier that it classically cannot surmount.

name

1. A locality in the City of Launceston, northern Tasmania, Australia.