Tunnel is a term used to describe a long, narrow PASSAGE that is dug through the ground or beneath a structure. An ADIT (4 letters) is a tunnel that is used for mining and is usually horizontal or nearly horizontal. An UNDERPASS (9 letters) is a tunnel that passes beneath a road or railway. A TUBE (4 letters) is a tunnel that is used for transportation, such as a SUBWAY (6 letters). A MINE (4 letters) is a tunnel that is dug into the ground to extract minerals or coal. A HOLE (4 letters) is a tunnel that is dug into the ground for various purposes. A PIT (3 letters) is a tunnel that is dug in the ground for the purpose of storing something. A PASSAGE (7 letters) is a tunnel that is used to connect two places. A SHAFT (5 letters) is a vertical tunnel that is used for ventilation or drainage. A BORE (4 letters) is a tunnel that is drilled through the ground. DIG (3 letters) is a verb meaning to make a tunnel by removing material from the ground. A BURROW (6 letters) is a tunnel that is dug by an animal, such as a MOLE (4 letters).