The Collaborative International Dictionary of English v.0.48:

Affiliate \Af*fil"i*ate\, v. t. [imp. & p. p. Affiliated; p.
   pr. & vb. n. Affiliating.] [LL. adfiliare, affiliare, to
   adopt as son; ad + filius son: cf. F. affilier.]
   1. To adopt; to receive into a family as a son; hence, to
      bring or receive into close connection; to ally.
      [1913 Webster]

            Is the soul affiliated to God, or is it estranged
            and in rebellion?                     --I. Taylor.
      [1913 Webster]

   2. To fix the paternity of; -- said of an illegitimate child;
      as, to affiliate the child to (or on or upon) one man
      rather than another.
      [1913 Webster]

   3. To connect in the way of descent; to trace origin to.
      [1913 Webster]

            How do these facts tend to affiliate the faculty of
            hearing upon the aboriginal vegetative processes?
                                                  --H. Spencer.
      [1913 Webster]

   4. To attach (to) or unite (with); to receive into a society
      as a member, and initiate into its mysteries, plans, etc.;
      -- followed by to or with.
      [1913 Webster]

   Affiliated societies, societies connected with a central
      society, or with each other.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Affiliate \Af*fil"i*ate\, v. i.
   To connect or associate one's self; -- followed by with; as,
   they affiliate with no party.
   [1913 Webster]

WordNet (r) 3.0 (2006):

affiliate
    n 1: a subordinate or subsidiary associate; a person who is
         affiliated with another or with an organization
    2: a subsidiary or subordinate organization that is affiliated
       with another organization; "network affiliates"
    v 1: keep company with; hang out with; "He associates with
         strange people"; "She affiliates with her colleagues" [syn:
         consort, associate, affiliate, assort]
    2: join in an affiliation; "The two colleges affiliated"; "They
       affiliated with a national group"

Moby Thesaurus II by Grady Ward, 1.0:

210 Moby Thesaurus words for "affiliate":
   Americanize, Anglicize, Greek, accept, acculturate, acculturize,
   act in concert, act together, admit, adopt, affiliate to,
   affiliate with, affiliated, allied, ally, amalgamate, approve, arm,
   assimilate, associate, associated, band, band together,
   be in cahoots, be in league, belonger, bound, bracketed, branch,
   branch office, brother, bunch, bunch up, cabal, cabalistic,
   card-carrier, card-carrying member, cardholder, carry,
   cement a union, centralize, chapter, charter member, club,
   club together, clubber, clubman, clubwoman, coact, coalesce,
   collaborate, collateral, collude, combine, come into,
   come together, committeeman, comrade, concert, concord, concur,
   confederate, confederated, confer citizenship, conjugate,
   connected, consociate, consolidate, conspiratorial, conspire,
   conventioneer, conventioner, conventionist, cooperate, corporate,
   correlated, couple, coupled, creep in, derive from, division,
   do business with, dues-paying member, embrace, enleagued, enlist,
   enlistee, enroll, enrollee, enter, espouse, father, federalize,
   federate, federated, fellow, filiate to, fraternity man, fuse,
   gang, gang up, get heads together, get into, get together,
   go in for, go in partners, go in partnership, go into, go native,
   go partners, guildsman, hang together, harmonize, hold together,
   honorary member, hook up, hook up with, implicated, in cahoots,
   in league, in partnership, in with, initiate, insider, interlinked,
   interlocked, interrelated, involved, join, join forces,
   join fortunes with, join in, join together, join up, join up with,
   join with, joined, joiner, keep together, knotted, league,
   league together, league with, leagued, life member, linked, local,
   lodge, make common cause, married, marry, member, merge,
   naturalize, of that ilk, of that kind, offshoot, one of us, organ,
   organize, pair, pair off, paired, parallel, partner, partners with,
   pass, play ball, pledge, post, pull together, put heads together,
   ratify, reciprocate, related, sign on, sign up, sister, sneak in,
   socius, sorority girl, sorority woman, spliced, stand together,
   stand up with, take out membership, take up, take up membership,
   team up, team up with, team with, teamed, throw in together,
   throw in with, tie in, tie in with, tie up, tie up with, tied,
   trace to, twinned, unionize, unite, unite efforts, unite with, wed,
   wedded, wing, work together, yoked