The Collaborative International Dictionary of English v.0.48:

Gyle \Gyle\ (g[imac]l), n. [F. guiller to ferment. Cf.
   Guillevat.]
   Fermented wort used for making vinegar.
   [1913 Webster]

   Gyle tun (Brewing), a large vat in which wort ferments.
      [1913 Webster]