The Collaborative International Dictionary of English v.0.48:

Immigrant \Im"mi*grant\, n. [L. immigrans, p. pr. of immigrare
   to go into: cf. F. immigrant. See Immigrate.]
   One who immigrates; one who comes to a country for the
   purpose of permanent residence; -- correlative of emigrant.

   Syn: See Emigrant.
        [1913 Webster]

WordNet (r) 3.0 (2006):

immigrant
    n 1: a person who comes to a country where they were not born in
         order to settle there

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "immigrant":
   DP, alien, arrival, arriviste, citizen, citizen by adoption,
   colonial, colonist, colonizer, comer, cosmopolitan, cosmopolite,
   displaced person, emigrant, emigre, entrant, evacue, evacuee,
   exile, expatriate, foreigner, gate-crasher, greenhorn, homesteader,
   hyphenate, hyphenated American, in-migrant, incomer, intruder,
   metic, migrant, migrator, migratory worker, national,
   naturalized citizen, nester, new arrival, new boy, newcomer,
   nonnative citizen, novus homo, out-migrant, outlander, outsider,
   parvenu, pioneer, planter, precursor, recruit, rookie, settler,
   sooner, squatter, stateless person, stowaway, subject, tenderfoot,
   trekker, upstart, visitant, visitor, wetback



The Devil's Dictionary (1881-1906):

IMMIGRANT, n.  An unenlightened person who thinks one country better
than another.