The Collaborative International Dictionary of English v.0.48:

Accede \Ac*cede"\, v. i. [imp. & p. p. Acceded; p. pr. & vb.
   n. Acceding.] [L. accedere to approach, accede; ad + cedere
   to move, yield: cf. F. acc['e]dere. See Cede.]
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   1. To approach; to come forward; -- opposed to recede.
      [Obs.] --T. Gale.
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   2. To enter upon an office or dignity; to attain.
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            Edward IV., who had acceded to the throne in the
            year 1461.                            --T. Warton.
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            If Frederick had acceded to the supreme power.
                                                  --Morley.
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   3. To become a party by associating one's self with others;
      to give one's adhesion. Hence, to agree or assent to a
      proposal or a view; as, he acceded to my request.
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            The treaty of Hanover in 1725 . . . to which the
            Dutch afterwards acceded.             --Chesterfield.
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   Syn: To agree; assent; consent; comply; acquiesce; concur.
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WordNet (r) 3.0 (2006):

accede
    v 1: yield to another's wish or opinion; "The government bowed
         to the military pressure" [syn: submit, bow, defer,
         accede, give in]
    2: take on duties or office; "accede to the throne" [syn:
       accede, enter]
    3: to agree or express agreement; "The Maestro assented to the
       request for an encore" [syn: assent, accede, acquiesce]
       [ant: dissent]