The Collaborative International Dictionary of English v.0.48:

Index \In"dex\, v. t. [imp. & p. p. Indexed; p. pr. & vb. n.
   Indexing.]
   1. To provide with an index or table of references; to put
      into an index; as, to index a book, or its contents.
      [1913 Webster]

   2. (Economics) To adjust (wages, prices, taxes, etc.)
      automatically so as to compensate for changes in prices,
      usually as measured by the consumer price index or other
      economic measure. Its purpose is usually to copensate for
      inflation.
      [PJC]

   3. To insert (a word, name, file folder, etc.) into an index
      or into an indexed arrangement; as, to index a contract
      under its date of signing.
      [PJC]

WordNet (r) 3.0 (2006):

indexing
    n 1: the act of classifying and providing an index in order to
         make items easier to retrieve