The Collaborative International Dictionary of English v.0.48:

Commemoration \Com*mem`o*ra"tion\, n. [L. commemoratio.]
   1. The act of commemorating; an observance or celebration
      designed to honor the memory of some person or event.
      [1913 Webster]

            This sacrament was designed to be a standing
            commemoration of the death and passion of our Lord.
                                                  --Abp.
                                                  Tillotson.
      [1913 Webster]

            The commonwealth which . . . chooses the most
            flagrant act of murderous regicide treason for a
            feast of eternal commemoration.       --Burke.
      [1913 Webster]

   2. Whatever serves the purpose of commemorating; a memorial.
      [1913 Webster]

   Commemoration day, at the University of Oxford, Eng., an
      annual observance or ceremony in honor of the benefactors
      of the University, at which time honorary degrees are
      conferred.
      [1913 Webster]

WordNet (r) 3.0 (2006):

commemoration
    n 1: a ceremony to honor the memory of someone or something
         [syn: commemoration, memorialization,
         memorialisation]
    2: a recognition of meritorious service [syn: memorial,
       commemoration, remembrance]