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]

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.