Adit

n.	1.	An entrance or passage. Specifically: The nearly horizontal opening by which a mine is entered, or by which water and ores are carried away; - called also drift and tunnel.
	2.	Admission; approach; access. Yourself and yours shall have Free adit. - Tennyson.

Noun

1.

adit - a nearly horizontal passage from the surface into a mine

access, admission, admittance, air lock, approach, channel, conduit, corridor, course, ditch, duct, egress, entrance, entranceway, entree, entry, entryway, exit, gangplank, gangway, hall, in, ingress, inlet, intake, means of access, opening, passage, passageway, trench, trough, troughing, troughway, tunnel, vestibule, way, way in