The Collaborative International Dictionary of English v.0.48:

Citizen \Cit"i*zen\, n. [OE. citisein, OF. citeain, F. citoyen,
   fr. cit['e] city. See City, and cf. Cit.]
   1. One who enjoys the freedom and privileges of a city; a
      freeman of a city, as distinguished from a foreigner, or
      one not entitled to its franchises.
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            That large body of the working men who were not
            counted as citizens and had not so much as a vote to
            serve as an anodyne to their stomachs. --G. Eliot.
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   2. An inhabitant of a city; a townsman. --Shak.
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   3. A person, native or naturalized, of either sex, who owes
      allegiance to a government, and is entitled to reciprocal
      protection from it.
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   Note: This protection is . . . national protection,
         recognition of the individual, in the face of foreign
         nations, as a member of the state, and assertion of his
         security and rights abroad as well as at home. --Abbot
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   4. One who is domiciled in a country, and who is a citizen,
      though neither native nor naturalized, in such a sense
      that he takes his legal status from such country.
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The Collaborative International Dictionary of English v.0.48:

Citizen \Cit"i*zen\, a.
   1. Having the condition or qualities of a citizen, or of
      citizens; as, a citizen soldiery.
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   2. Of or pertaining to the inhabitants of a city;
      characteristic of citizens; effeminate; luxurious. [Obs.]
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            I am not well,
            But not so citizen a wanton as
            To seem to die ere sick.              --Shak.
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WordNet (r) 3.0 (2006):

citizen
    n 1: a native or naturalized member of a state or other
         political community [ant: alien, foreigner,
         noncitizen, outlander]