The Collaborative International Dictionary of English v.0.48:

Thurl \Thurl\, n. [AS. [thorn]yrel a hole. [root]53. See
   Thirl, Thrill.]
   1. A hole; an aperture. [Obs.]
      [1913 Webster]

   2. (Mining)
      (a) A short communication between adits in a mine.
      (b) A long adit in a coalpit.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thurl \Thurl\, v. t. [See Thrill.]
   1. To cut through; to pierce. [Obs.] --Piers Plowman.
      [1913 Webster]

   2. (Mining) To cut through, as a partition between one
      working and another.
      [1913 Webster]