The Collaborative International Dictionary of English v.0.48:

Agree \A*gree"\, v. i. [imp. & p. p. Agreed; p. pr. & vb. n.
   Agreeing.] [F. agr['e]er to accept or receive kindly, fr.
   [`a] gr['e]; [`a] (L. ad) + gr['e] good will, consent,
   liking, fr. L. gratus pleasing, agreeable. See Grateful.]
   1. To harmonize in opinion, statement, or action; to be in
      unison or concord; to be or become united or consistent;
      to concur; as, all parties agree in the expediency of the
      law.
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            If music and sweet poetry agree.      --Shak.
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            Their witness agreed not together.    --Mark xiv.
                                                  56.
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            The more you agree together, the less hurt can your
            enemies do you.                       --Sir T.
                                                  Browne.
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   2. To yield assent; to accede; -- followed by to; as, to
      agree to an offer, or to opinion.
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   3. To make a stipulation by way of settling differences or
      determining a price; to exchange promises; to come to
      terms or to a common resolve; to promise.
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            Agree with thine adversary quickly.   --Matt. v. 25.
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            Didst not thou agree with me for a penny ? --Matt.
                                                  xx. 13.
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   4. To be conformable; to resemble; to coincide; to
      correspond; as, the picture does not agree with the
      original; the two scales agree exactly.
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   5. To suit or be adapted in its effects; to do well; as, the
      same food does not agree with every constitution.
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   6. (Gram.) To correspond in gender, number, case, or person.
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   Note: The auxiliary forms of to be are often employed with
         the participle agreed. "The jury were agreed."
         --Macaulay. "Can two walk together, except they be
         agreed ?" --Amos iii. 3. The principal intransitive
         uses were probably derived from the transitive verb
         used reflexively. "I agree me well to your desire."
         --Ld. Berners.
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   Syn: To assent; concur; consent; acquiesce; accede; engage;
        promise; stipulate; contract; bargain; correspond;
        harmonize; fit; tally; coincide; comport.
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WordNet (r) 3.0 (2006):

agreed
    adj 1: united by being of the same opinion; "agreed in their
           distrust of authority" [syn: agreed, in agreement(p)]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "agreed":
   OK, acquiescent, acquiescing, agreeing, all right, amen, arranged,
   assentatious, assenting, aye, be it so, compacted, compliant,
   conceding, concessive, consenting, content, contracted, covenanted,
   done, engaged, promised, sealed, settled, signed, so be it,
   so is it, so it is, stipulated, submissive, undertaken, yea, yep,
   you bet