The Collaborative International Dictionary of English v.0.48:

United \U*nit"ed\, a.
   Combined; joined; made one.
   [1913 Webster]

   United Brethren. (Eccl.) See Moravian, n.

   United flowers (Bot.), flowers which have the stamens and
      pistils in the same flower.

   The United Kingdom, Great Britain and Ireland; -- so named
      since January 1, 1801, when the Legislative Union went
      into operation.

   United Greeks (Eccl.), those members of the Greek Church
      who acknowledge the supremacy of the pope; -- called also
      uniats.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Unite \U*nite"\, v. t. [imp. & p. p. United; p. pr. & vb. n.
   Uniting.] [L. unitus, p. p. of unire to unite, from unus
   one. See One.]
   1. To put together so as to make one; to join, as two or more
      constituents, to form a whole; to combine; to connect; to
      join; to cause to adhere; as, to unite bricks by mortar;
      to unite iron bars by welding; to unite two armies.
      [1913 Webster]

   2. Hence, to join by a legal or moral bond, as families by
      marriage, nations by treaty, men by opinions; to join in
      interest, affection, fellowship, or the like; to cause to
      agree; to harmonize; to associate; to attach.
      [1913 Webster]

            Under his great vicegerent reign abide,
            United as one individual soul.        --Milton.
      [1913 Webster]

            The king proposed nothing more than to unite his
            kingdom in one form of worship.       --Clarendon.
      [1913 Webster]

   Syn: To add; join; annex; attach. See Add.
        [1913 Webster]

WordNet (r) 3.0 (2006):

united
    adj 1: characterized by unity; being or joined into a single
           entity; "presented a united front" [ant: divided]
    2: of or relating to two people who are married to each other
       [syn: joined, united]

Moby Thesaurus II by Grady Ward, 1.0:

125 Moby Thesaurus words for "united":
   accompanying, accordant, agreeable, agreed, agreeing, akin, allied,
   amalgamated, amicable, assembled, assimilated, associate,
   associated, at one, at one with, attuned, banded together, blended,
   bound, bracketed, coacting, coactive, coadunate, coalesced,
   coincident, collaborative, collected, collective, collusive,
   combinative, combinatory, combined, combining, common, communal,
   compatible, composite, concerted, concomitant, concordant,
   concurrent, concurring, congenial, conjoined, conjoint, conjugate,
   conjunctive, connected, connective, consilient, consolidated,
   conspiratorial, cooperant, cooperative, coordinate, coordinated,
   copulate, corresponding, coupled, coworking, eclectic, empathetic,
   empathic, en rapport, frictionless, fused, gathered, hand-in-glove,
   hand-in-hand, harmonious, in accord, in agreement, in concert,
   in harmony, in rapport, in tune, incorporated, inharmony, integral,
   integrant, integrated, intimate, joined, joint, knotted, leagued,
   like-minded, linked, matched, mated, meeting, merged, mixed,
   mutual, of like mind, of one mind, one, paired, parasitic,
   partnership, peaceful, rolled into one, saprophytic, shared,
   spliced, symbiotic, sympathetic, synchronous, syncretistic,
   syncretized, synergetic, synergic, synergistic, synthesized, tied,
   together, unanimous, understanding, undivided, unified, unitary,
   uniting, unseparated, wedded, yoked