The Collaborative International Dictionary of English v.0.48:

Denizen \Den"i*zen\ (d[e^]n"[i^]*z'n), n. [OF. denzein,
   deinzein, prop., one living (a city or country); opposed to
   forain foreign, and fr. denz within, F. dans, fr. L. de
   intus, prop., from within, intus being from in in. See In,
   and cf. Foreign.]
   1. A dweller; an inhabitant. "Denizens of air." --Pope.
      [1913 Webster]

            Denizens of their own free, independent state. --Sir
                                                  W. Scott.
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   2. One who is admitted by favor to all or a part of the
      rights of citizenship, where he did not possess them by
      birth; an adopted or naturalized citizen.
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   3. One admitted to residence in a foreign country.
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            Ye gods,
            Natives, or denizens, of blest abodes. --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Denizen \Den"i*zen\, v. t.
   1. To constitute (one) a denizen; to admit to residence, with
      certain rights and privileges.
      [1913 Webster]

            As soon as denizened, they domineer.  --Dryden.
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   2. To provide with denizens; to populate with adopted or
      naturalized occupants.
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            There [islets] were at once denizened by various
            weeds.                                --J. D.
                                                  Hooker.
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WordNet (r) 3.0 (2006):

denizen
    n 1: a person who inhabits a particular place [syn:
         inhabitant, habitant, dweller, denizen,
         indweller]
    2: a plant or animal naturalized in a region; "denizens of field
       and forest"; "denizens of the deep"

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "denizen":
   addressee, artist-in-residence, citizen, colonize, dweller,
   empeople, frequenter, habitant, haunter, house detective,
   incumbent, inhabit, inhabitant, inhabiter, inmate, inpatient,
   intern, live-in maid, liver, locum tenens, national, occupant,
   occupier, people, plant, populate, residencer, resident,
   resident physician, residentiary, resider, settle, settle in,
   sojourner, subject, tenant



Bouvier's Law Dictionary, Revised 6th Ed (1856):

DENIZEN, English law. An alien born, who has obtained, ex donatione legis,
letters patent to make him au English subject.
     2. He is intermediate between a natural born subject and an alien. He
may. take lands by purchase or devise, which an alien cannot, but he is
incapable of taking by inheritance. 1 Bl. Com. 374. In the United States
there is no such civil condition.