also: おうこう
noun
adit; horizontal mine tunnel
Technical term in mining and civil engineering for a nearly horizontal passage into a mine, used for access, drainage, or ventilation.
この鉱山には古い横坑がいくつも残っている。
Many old adits remain in this mine.
横坑から排水が行われている。
Drainage is carried out from the adit.
Irregular reading; marked as 'irregular kana usage'. Learners should use よここう.
Compound of 横 (horizontal) and 坑 (mine/pit). The reading おうこう is irregular and likely a less common variant.