The Collaborative International Dictionary of English v.0.48:

Adjuration \Ad`ju*ra"tion\, n. [L. adjuratio, fr. adjurare: cf.
   F. adjuration. See Adjure.]
   1. The act of adjuring; a solemn charging on oath, or under
      the penalty of a curse; an earnest appeal.
      [1913 Webster]

            What an accusation could not effect, an adjuration
            shall.                                --Bp. Hall.
      [1913 Webster]

   2. The form of oath or appeal.
      [1913 Webster]

            Persons who . . . made use of prayer and
            adjurations.                          --Addison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

adjuration
    n 1: a solemn and earnest appeal to someone to do something