plural tunnels
: a passage that goes under the ground, through a hill, etc.
an underground tunnel
The train goes through a tunnel in the mountain.
The moles dug tunnels in the yard.
tunnels; US tunneled or British tunnelled; US tunneling or British tunnelling
: to make a tunnel
Workers are tunneling through the hill.
Insects had tunneled into the tree.
The prisoners tried to tunnel their way out. [=tried to escape by digging a tunnel]
Cite this Entry
“Tunnel.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/tunnel. Accessed 16 Apr. 2026.
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