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

The Devil's Dictionary (1881-1906):

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