The Collaborative International Dictionary of English v.0.48:

Anniversary \An`ni*ver"sa*ry\, a. [L. anniversarius; annus year
   + vertere, versum, to turn: cf. F. anniversaire.]
   Returning with the year, at a stated time; annual; yearly;
   as, an anniversary feast.
   [1913 Webster]

   Anniversary day (R. C. Ch.). See Anniversary, n., 2.

   Anniversary week, that week in the year in which the annual
      meetings of religious and benevolent societies are held in
      Boston and New York. [Eastern U. S.]
      [1913 Webster]