Webster's Revised Unabridged Dictionary · 1913

Thurl

Thurl , noun

[Anglo-Saxon þyrel a hole. r53. See Thirl, Thrill.]

1.
A hole; an aperture. [Obsolete]
2.
(a) (Mining) A short communication between adits in a mine.
(b)
(Mining) A long adit in a coalpit.

Thurl , transitive verb

[See Thrill.]

1.
To cut through; to pierce. [Obsolete] — Piers Plowman
2.
(Mining) To cut through, as a partition between one working and another.