tunnel

The word “tunnel” means an underground or underwater passage, often built for travel. In plain terms, a passage dug through or under something — literally underground, or figuratively in computing, where data is "tunneled" securely through another connection.

“Tunnel” is pronounced TUHNL (/ˈtʌn(ə)l/ in IPA).

Here is “tunnel” used in a sentence: “The train disappeared into a long tunnel through the mountain.”

Depending on how it is used, “tunnel” can be a noun and a verb.

The word “tunnel” comes from Middle French. From Middle French tonnelle ("net") or tonel ("cask"), related to Old English tunne, the ancestor of "tun.".

“Tunnel” is a fairly common word in modern English, usually learned at around the B2 level.

“Tunnel” has 3 distinct senses listed in this dictionary. The most common is: an underground or underwater passage, often built for travel.

A tunnel is a passage that is deliberately dug or built through or under something, usually for travel, whereas a cave is a natural hollow formed in rock or the ground. In short, tunnels are man-made while caves occur naturally, though a natural cave can sometimes be widened into a tunnel.

A tunnel is a passage dug or built through or under something, often large enough for vehicles, trains, or people, while a burrow is a hole or tunnel dug in the ground by an animal such as a rabbit for shelter. 'Burrow' almost always refers to animal-made holes, whereas 'tunnel' covers both engineered passages and the act of digging them.

Both are correct depending on the variety of English: British English doubles the L to give 'tunnelling' and 'tunnelled', while American English usually keeps a single L as 'tunneling' and 'tunneled'. The base noun and verb 'tunnel' are spelled the same in both.