Webster's Revised Unabridged Dictionary · 1913

adit

adit (ad"it) , noun

[Latin aditus, from adire, aditum, to go to; ad + ire to go.]

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. [Rare]
Yourself and yours shall have Free adit. — Tennyson