adit
noun
ad·it ˈa-dət 
: a nearly horizontal passage from the surface in a mine
Example Sentences
Recent Examples on the Web The second phase will involve closing the mine’s adits and shafts. 
USA TODAY, 27 June 2019
USA TODAY, 27 June 2019 Word History
Etymology
borrowed from Latin aditus "approach, entrance," from adi-, stem of adīre "to go to, approach" (from ad- ad- + īre "to go") + -tus, suffix of action nouns — more at issue entry 1
First Known Use
1602, in the meaning defined above