The Collaborative International Dictionary of English v.0.48:

Constitution \Con`sti*tu"tion\ (k[o^]n`st[i^]*t[=u]"sh[u^]n), n.
   [F. constitution, L. constitutio.]
   1. The act or process of constituting; the action of
      enacting, establishing, or appointing; enactment;
      establishment; formation.
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   2. The state of being; that form of being, or structure and
      connection of parts, which constitutes and characterizes a
      system or body; natural condition; structure; texture;
      conformation.
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            The physical constitution of the sun. --Sir J.
                                                  Herschel.
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   3. The aggregate of all one's inherited physical qualities;
      the aggregate of the vital powers of an individual, with
      reference to ability to endure hardship, resist disease,
      etc.; as, a robust constitution.
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            Our constitutions have never been enfeebled by the
            vices or luxuries of the old world.   --Story.
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   4. The aggregate of mental qualities; temperament.
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            He defended himself with . . . less passion than was
            expected from his constitution.       --Clarendon.
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   5. The fundamental, organic law or principles of government
      of men, embodied in written documents, or implied in the
      institutions and usages of the country or society; also, a
      written instrument embodying such organic law, and laying
      down fundamental rules and principles for the conduct of
      affairs.
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            Our constitution had begun to exist in times when
            statesmen were not much accustomed to frame exact
            definitions.                          --Macaulay.
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   Note: In England the constitution is unwritten, and may be
         modified from time to time by act of Parliament. In the
         United States a constitution cannot ordinarily be
         modified, exept through such processes as the
         constitution itself ordains.
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   6. An authoritative ordinance, regulation or enactment;
      especially, one made by a Roman emperor, or one affecting
      ecclesiastical doctrine or discipline; as, the
      constitutions of Justinian.
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            The positive constitutions of our own churches.
                                                  --Hooker.
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            A constitution of Valentinian addressed to Olybrius,
            then prefect of Rome, for the regulation of the
            conduct of advocates.                 --George Long.
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   Apostolic constitutions. See under Apostolic.
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WordNet (r) 3.0 (2006):

constitution
    n 1: law determining the fundamental political principles of a
         government [syn: fundamental law, organic law,
         constitution]
    2: the act of forming or establishing something; "the
       constitution of a PTA group last year"; "it was the
       establishment of his reputation"; "he still remembers the
       organization of the club" [syn: constitution,
       establishment, formation, organization, organisation]
    3: the constitution written at the Constitutional Convention in
       Philadelphia in 1787 and subsequently ratified by the
       original thirteen states [syn: United States Constitution,
       U.S. Constitution, US Constitution, Constitution,
       Constitution of the United States]
    4: the way in which someone or something is composed [syn:
       constitution, composition, physical composition,
       makeup, make-up]
    5: a United States 44-gun frigate that was one of the first
       three naval ships built by the United States; it won
       brilliant victories over British frigates during the War of
       1812 and is without doubt the most famous ship in the history
       of the United States Navy; it has been rebuilt and is
       anchored in the Charlestown Navy Yard in Boston [syn:
       Constitution, Old Ironsides]