The Collaborative International Dictionary of English v.0.48:

Commonweal \Com"mon*weal"\, n. [Common + weal.]
   Commonwealth.
   [1913 Webster]

         Such a prince,
         So kind a father of the commonweal.      --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

commonweal
    n 1: the good of a community [syn: common good, commonweal]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "commonweal":
   ally, archduchy, archdukedom, body politic, buffer state,
   captive nation, chieftaincy, chieftainry, child welfare,
   city-state, colony, commonwealth, country, county, domain,
   dominion, duchy, dukedom, earldom, empery, empire, free city,
   grand duchy, kingdom, land, mandant, mandate, mandated territory,
   mandatee, mandatory, nation, nationality, polis, polity,
   possession, power, principality, principate, protectorate,
   province, public welfare, puppet government, puppet regime, realm,
   republic, satellite, seneschalty, settlement, social service,
   social welfare, social work, sovereign nation, state, sultanate,
   superpower, territory, toparchia, toparchy, welfare, welfare state,
   welfare statism, welfare work, welfarism