The Collaborative International Dictionary of English v.0.48:

Relational \Re*la"tion*al\ (r?-l?"sh?n-al), a.
   1. Having relation or kindred; related.
      [1913 Webster]

            We might be tempted to take these two nations for
            relational stems.                     --Tooke.
      [1913 Webster]

   2. Indicating or specifying some relation.
      [1913 Webster]

            Relational words, as prepositions, auxiliaries, etc.
                                                  --R. Morris.
      [1913 Webster]

WordNet (r) 3.0 (2006):

relational
    adj 1: having a relation or being related