The Collaborative International Dictionary of English v.0.48:

Abjuration \Ab`ju*ra"tion\, n. [L. abjuratio: cf. F.
   abjuration.]
   1. The act of abjuring or forswearing; a renunciation upon
      oath; as, abjuration of the realm, a sworn banishment, an
      oath taken to leave the country and never to return.
      [1913 Webster]

   2. A solemn recantation or renunciation; as, an abjuration of
      heresy.
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   Oath of abjuration, an oath asserting the right of the
      present royal family to the crown of England, and
      expressly abjuring allegiance to the descendants of the
      Pretender. --Brande & C.
      [1913 Webster]