auto, automobile, car, motorcar, machine - 4-wheeled motor vehicle; usually propelled by an internal combustion engine; "he needs a car to get to work"

catacomb - an underground tunnel with recesses where bodies were buried (as in ancient Rome)

passageway - a passage between rooms or between buildings

railroad tunnel - a tunnel through which the railroad track runs

underpass, subway - an underground tunnel or passage enabling pedestrians to cross a road or railway

hollow, hole - a depression hollowed out of solid matter

rabbit warren, warren - a series of connected underground tunnels occupied by rabbits

cut into, delve, dig, turn over - turn up, loosen, or remove earth; "Dig we must"; "turn over the soil for aeration"

penetrate, perforate - pass into or through, often by overcoming resistance; "The bullet penetrated her chest"