The Collaborative International Dictionary of English v.0.48:

Concordance \Con*cord"ance\, n. [F., fr. LL. concordantia.]
   1. Agreement; accordance.
      [1913 Webster]

            Contrasts, and yet concordances.      --Carlyle.
      [1913 Webster]

   2. (Gram.) Concord; agreement. [Obs.] --Aschlam.
      [1913 Webster]

   3. An alphabetical verbal index showing the places in the
      text of a book where each principal word may be found,
      with its immediate context in each place.
      [1913 Webster]

            His knowledge of the Bible was such, that he might
            have been called a living concordance. --Macaulay.
      [1913 Webster]

   4. A topical index or orderly analysis of the contents of a
      book.
      [1913 Webster]

WordNet (r) 3.0 (2006):

concordance
    n 1: a harmonious state of things in general and of their
         properties (as of colors and sounds); congruity of parts
         with one another and with the whole [syn: harmony,
         concord, concordance]
    2: agreement of opinions [syn: harmony, concord,
       concordance]
    3: an index of all main words in a book along with their
       immediate contexts