Source : Webster's Revised Unabridged Dictionary (1913)

Durance \Dur"ance\, n. [OF. durance duration, fr. L. durans,
   -antis, p. pr. durare to endure, last. See {Dure}, and cf.
   {Durant}.]
   1. Continuance; duration. See {Endurance}. [Archaic]

            Of how short durance was this new-made state!
                                                  --Dryden.

   2. Imprisonment; restraint of the person; custody by a
      jailer; duress. Shak. ``Durance vile.'' --Burns.

            In durance, exile, Bedlam or the mint. --Pope.

   3.
      (a) A stout cloth stuff, formerly made in imitation of
          buff leather and used for garments; a sort of tammy or
          everlasting.

                Where didst thou buy this buff? let me not live
                but I will give thee a good suit of durance.
                                                  --J. Webster.
      (b) In modern manufacture, a worsted of one color used for
          window blinds and similar purposes.

Source : WordNet®

durance
     n : imprisonment (especially for a long time)