Source : Webster's Revised Unabridged Dictionary (1913)

Jury \Ju"ry\, a. [Etymol. uncertain.] (Naut.)
   For temporary use; -- applied to a temporary contrivance.

   {Jury mast}, a temporary mast, in place of one that has been
      carried away, or broken.

   {Jury rudder}, a rudder constructed for temporary use.

Jury mast \Ju"ry mast\
   (a) A temporary mast, in place of one that has been carried
       away, or broken.
   (b) (Med.) An apparatus to support the trunk and head in
       spinal disease.

Source : WordNet®

jury mast
     n : a temporary mast to replace one that has broken off