The Collaborative International Dictionary of English v.0.48:

Affiliation \Af*fil`i*a"tion\, n. [F. affiliation, LL.
   affiliatio.]
   1. Adoption; association or reception as a member in or of
      the same family or society.
      [1913 Webster]

   2. (Law) The establishment or ascertaining of parentage; the
      assignment of a child, as a bastard, to its father;
      filiation.
      [1913 Webster]

   3. Connection in the way of descent. --H. Spencer.
      [1913 Webster]

WordNet (r) 3.0 (2006):

affiliation
    n 1: a social or business relationship; "a valuable financial
         affiliation"; "he was sorry he had to sever his ties with
         other members of the team"; "many close associations with
         England" [syn: affiliation, association, tie, tie-
         up]
    2: the act of becoming formally connected or joined; "welcomed
       the affiliation of the research center with the university"