tunnel

Pluraltunnels

Formstunnels

1. 1
   nouncountable

   An underground or underwater passage, often built for roads, trains, or pedestrians.

   Commuters poured into the tunnel during the evening rush.

   Engineers spent years boring the rail tunnel through solid rock.

   Similarunderpass, passage, subway

   Note

   A word that began among barrels, not underground. It comes from Middle French tonnelle ("net") or tonel ("cask"), small forms of Old French tonne, "cask", and is related to Old English tunne and modern tun. A tunnel can carry its builder's name. Andrew Martin's Underground Overground (2012) tells how the Brunel tunnel was bought in 1865 and had trains running through it by 1869.

2. 2
   nouncountable

   A passage made through or under an obstacle that stands in the way.

   Workers carved a tunnel through the rockfall to clear the blocked road.

   A narrow tunnel beneath the wall let the sheep pass into the next field.

   Similarpassage, passageway, underpass

   Note

   Here the point is what the passage gets past, not whether it lies underground. The obstacle may be a hill: Tim Dunn counts more than 1,500 railway tunnels beneath Britain's "most inconvenient geographic features." It may also be as soft as bedclothes, where the Boy in Margery Williams's The Velveteen Rabbit (1921) makes tunnels for his toy. The prepositions that go with it are through and under.

3. 3
   verbintransitive

   To dig a tunnel through or under the ground.

   The crew will tunnel beneath the harbor over the next two years.

   Escapees tunneled under the fence during the long winter nights.

   Similardig, burrow, bore, excavate, mine

4. 4
   verbtransitive

   To dig a passage through or beneath something; to burrow.

   The company plans to tunnel the ridge for a new mountain highway.

   Crews tunneled the embankment to install the drainage line.

   Similarburrow, dig, undermine

   Note

   Spelling splits along the Atlantic. American English writes tunneled and tunneling with one l, while British English doubles it to tunnelled and tunnelling. In use the verb leans on under and beneath, as when a planned rail link would tunnel under the M25 to reach Heathrow. Its synonym undermine shares the same picture of digging beneath something.

5. 5
   nouncountable

   A hole in the ground dug by an animal, also called a burrow.

   The fox bolted down the tunnel at the first sound of the hounds.

   Earthworms leave tiny tunnels throughout the topsoil.

   Similarburrow, hole

6. 6
   nounfigurativelycountable

   Something that resembles a tunnel in shape or form.

   The overhanging branches created a leafy tunnel above the footpath.

   She felt as if she were staring down a long tunnel of old memories.

   Similarcorridor, passage

7. 7
   nouncountable

   A wrapper for a network protocol that lets it travel when it would otherwise be unsupported, blocked, or insecure.

   Like shipping a fragile package inside a sturdy crate so it survives a journey it couldn't make on its own.

   Administrators route the blocked traffic through an encrypted tunnel.

   The application opens a tunnel so the older data can cross the firewall safely.

   Note

   A networking metaphor borrowed from the passage through an obstacle: one protocol is wrapped inside another, so traffic a network would refuse, could not carry, or would leave exposed crosses it as something permitted. The tunnel is the wrapping, not a physical route. Data is sent through a tunnel, and the act of sending it that way has its own verb, to tunnel traffic.

8. 8
   verbtransitive

   To transmit data through a tunnel, wrapping it so it can cross networks that would block or fail to carry it.

   Like passing a message in a code that travels safely along a route the plain message could never take.

   Engineers tunnel the legacy protocol over a modern encrypted link.

   The client tunnels all of its requests through a single secure port.

   Similarencapsulate, route

   Note

   Two things meet in this verb: what is carried and what carries it. Engineers tunnel one protocol over another, or tunnel requests through a single port, so the preposition names the outer layer. It is the action behind the networking noun. The verb works without any digging at all: nothing is bored through, only wrapped and passed along.

9. 9
   verbintransitive

   Of a particle, to pass through an energy barrier that it could not cross according to classical physics.

   Like a ball that, against all expectation, sometimes appears on the far side of a wall it never went over.

   At the atomic scale, electrons tunnel through barriers that classical physics forbids.

   Particles occasionally tunnel past energy walls instead of climbing over them.

   Note

   Physics uses the word for a crossing that no digging could explain. A particle gets through a barrier higher than its own energy, an outcome classical mechanics forbids. The contrast to keep in mind is with over: classically a particle must climb over a barrier or turn back, while to tunnel is to arrive on the far side without the energy to climb.

10. 10
    nouncountable

    The opening of a chimney through which smoke passes; a flue.

    The sweep cleared the tunnel of years of caked soot.

    Warm air drew the smoke up the narrow tunnel of the hearth.

    Similarflue

    Note

    A smoke passage that still wore its French spelling in Edmund Spenser's The Faerie Queene (1590): "one great chimney, whose long tonnell thence, / The smoke forth threw." Spenser's spelling, tonnell, sits close to Middle French tonnelle. His chimney's passage is also long, which suits the word better than a mere opening would.

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