English Reference

Word

tunnel

Phoneticstun·nel

US/ˈtənəɫ/

UK/tˈʌnəl/

US spelling · tunneled

Definitions

01underground passage

B1

n. a long passage built under the ground, through a hill, or under a river for cars, trains, or people.

n. an artificial underground or underwater passage, typically constructed for transportation or utility infrastructure.

“The train went through a long tunnel under the mountains.”

“Engineers spent nearly a decade constructing the undersea tunnel to connect the two islands, overcoming significant geological challenges along the way.”

Synonyms

passageunderpasssubway

02animal burrow

B2

n. a long hole in the ground made by an animal to live in or move through.

n. a subterranean passage or burrow excavated by an animal for habitation or transit.

“The rabbit disappeared into a small tunnel near the edge of the field.”

“The garden was riddled with complex tunnels created by moles, which had significantly damaged the root systems of the prize-winning roses.”

Synonyms

03computing

C1 · Computing

n. a safe way to send data over the internet by hiding it inside another type of data.

n. a communication protocol that allows for the movement of data from one network to another by encapsulating one protocol within another.

“He used a secure tunnel to access his office files from home.”

“The network administrator established an SSH tunnel to bypass the restrictive firewall and manage the remote server securely.”

Technical

Synonyms

04to dig a passage

B2

v. to dig a long hole under or through something.

v. to excavate a tunnel through or under a physical barrier. Often used with 'through' or 'under'.

“The prisoners tried to tunnel under the wall to escape.”

“The construction crew had to tunnel through solid granite to complete the new highway extension before the winter deadline.”

Synonyms

digburrowexcavate

05physics

C2 · Science

v. when a tiny particle passes through a barrier that it normally should not be able to cross.

v. to undergo the quantum-mechanical phenomenon where a particle penetrates a potential energy barrier that it classically lacks the energy to surmount.

“In quantum physics, particles can sometimes tunnel through barriers.”

“Quantum tunneling is a fundamental process in nuclear fusion, allowing protons to overcome their mutual electrostatic repulsion despite having insufficient kinetic energy.”

Technical

Real-World Examples

“Nepal rescuers send air pipe into tunnel with trapped workers.”
The Guardian · 29 Aug 2026
“We drink coffee and watch the children dig tunnels in the sand.”
The Guardian · 23 Aug 2026

Etymology

From Middle French tonnelle (“net”) or tonel (“cask”), diminutive of Old French tonne (“cask”), a word of uncertain origin and affiliation. Related to Old English tunne (“tun; cask; barrel”). More at tun.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Idioms

ear tunnel — A round piece of jewelry with a hole in the middle, which fits into a stretched earlobe.

light at the end of the tunnel — A better situation after long hardship.

quantum tunnel — To move or travel from one point or direction to another in a very quick, rapid, or effortless manner.

wind tunnel testing — The application of a rigorous testing regime to a new corporate idea, structure or project to determine if it is viable and fit for purpose.

Domains

ComputingMedicineMiningPhysics

This entry

Level
B2 · Upper Intermediate
Frequency
Common
Updated

Scan code

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English Reference