Source : Webster's Revised Unabridged Dictionary (1913)

Commonwealth \Com"mon*wealth`\ (?; 277), n. [Common + wealth
   well-being.]
   1. A state; a body politic consisting of a certain number of
      men, united, by compact or tacit agreement, under one form
      of government and system of laws.

            The trappings of a monarchy would set up an ordinary
            commonwealth.                         --Milton.

   Note: This term is applied to governments which are
         considered as free or popular, but rarely, or
         improperly, to an absolute government. The word
         signifies, strictly, the common well-being or
         happiness; and hence, a form of government in which the
         general welfare is regarded rather than the welfare of
         any class.

   2. The whole body of people in a state; the public.

   3. (Eng. Hist.) Specifically, the form of government
      established on the death of Charles I., in 1649, which
      existed under Oliver Cromwell and his son Richard, ending
      with the abdication of the latter in 1659.

   Syn: State; realm; republic.

Source : WordNet®

commonwealth
     n 1: the official name of some states in the United States
          (Massachusetts and Pennsylvania and Virginia and
          Kentucky) and associated territories (Puerto Rico)
     2: a politically organized body of people under a single
        government; "the state has elected a new president";
        "African nations"; "students who had come to the nation's
        capitol"; "the country's largest manufacturer"; "an
        industrialized land" [syn: {state}, {nation}, {country}, {land},
         {res publica}, {body politic}]
     3: a world organization of autonomous states that are united in
        allegiance to a central power but are not subordinate to
        it or to one another
     4: a political system in which the supreme power lies in a body
        of citizens who can elect people to represent them [syn: {democracy},
         {republic}] [ant: {autocracy}]