The Collaborative International Dictionary of English v.0.48:

Abdication \Ab`di*ca"tion\, n. [L. abdicatio: cf. F.
   abdication.]
   The act of abdicating; the renunciation of a high office,
   dignity, or trust, by its holder; commonly the voluntary
   renunciation of sovereign power; as, abdication of the
   throne, government, power, authority.
   [1913 Webster]

WordNet (r) 3.0 (2006):

abdication
    n 1: a formal resignation and renunciation of powers [syn:
         abdication, stepping down]
    2: the act of abdicating [syn: abdication, stepping down]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "abdication":
   abjuration, abjurement, cession, demission, deposal, dropping out,
   emeritus status, forced resignation, forswearing, handing over,
   relinquishment, renouncement, renunciation, resignation, retiral,
   retirement, superannuation, surrender, voluntary resignation,
   waiver, withdrawal, withdrawing, yielding



Bouvier's Law Dictionary, Revised 6th Ed (1856):

ABDICATION, government. 1. A simple renunciation of an office, generally
understood of a supreme office. James II. of England; Charles V. of Germany;
and Christiana, Queen of Sweden, are said to have abdicated.  When James III
of England left the kingdom, the Commons voted that he had abdicated the
government, and that thereby the throne had become vacant.  The House of
Lords preferred the word deserted, but the Commons thought it not
comprehensive enough, for then, the king might have the liberty of
returning. 2. When inferior magistrates decline or surrender their offices,
they are said to make a resignation. (q.v.)



The Devil's Dictionary (1881-1906):

ABDICATION, n.  An act whereby a sovereign attests his sense of the
high temperature of the throne.

    Poor Isabella's Dead, whose abdication
    Set all tongues wagging in the Spanish nation.
    For that performance 'twere unfair to scold her:
    She wisely left a throne too hot to hold her.
    To History she'll be no royal riddle --
    Merely a plain parched pea that jumped the griddle.
                                                                  G.J.