The Collaborative International Dictionary of English v.0.48:

Gaol \Gaol\ (j[=a]l), n. [See Jail.]
   A place of confinement, especially for minor offenses or
   provisional imprisonment; a jail. [Preferably, and in the
   United States usually, written jail.]
   [1913 Webster]

   Commission of general gaol delivery, an authority conferred
      upon judges and others included in it, for trying and
      delivering every prisoner in jail when the judges, upon
      their circuit, arrive at the place for holding court, and
      for discharging any whom the grand jury fail to indict.
      [Eng.]

   Gaol delivery. (Law) See Jail delivery, under Jail.
      [1913 Webster]