The Collaborative International Dictionary of English v.0.48:

commemorating \commemorating\ adj.
   of or pertaining to a commemoration; serving to commemorate.

   Syn: commemorative.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Commemorate \Com*mem"o*rate\, v. t. [imp. & p. p.
   Commemorated; p. pr. & vb. n. Commemorating.] [L.
   commemoratus, p. p. of commemorare to remember; com- +
   memorare to mention, fr. memor mindful. See Memory.]
   To call to remembrance by a special act or observance; to
   celebrate with honor and solemnity; to honor, as a person or
   event, by some act of respect or affection, intended to
   preserve the remembrance of the person or event; as, to
   commemorate the sufferings and dying love of our Savior by
   the sacrament of the Lord's Supper; to commemorate the
   Declaration of Independence by the observance of the Fourth
   of July.
   [1913 Webster]

         We are called upon to commemorate a revolution.
                                                  --Atterbury.

   Syn: See Celebrate.
        [1913 Webster]

WordNet (r) 3.0 (2006):

commemorating
    adj 1: intended as a commemoration; "a commemorative plaque"
           [syn: commemorative, commemorating]