1. an underground or underwater passage
2. a covered passage through or under an obstacle

1. to dig or bore a tunnel
2. to make a way through or under something

Examples

• The train passed through a long tunnel under the mountain.
• Workers are building a tunnel beneath the river.
• The subway tunnel connects the two stations.
• Miners tunneled deep into the earth searching for gold.
• The prisoners tunneled under the prison wall to escape.
• Moles tunnel through the ground looking for food.
• Engineers will tunnel through the hill to build the highway.