The Collaborative International Dictionary of English v.0.48:

Migrant \Mi"grant\, a. [L. migrans, p. pr. of migrare. See
   Migrate.]
   Migratory. --Sir T. Browne.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Migrant \Mi"grant\, n.
   1. A migratory bird, person, or other animal.

   2. A person who changes residence frequently in search of
      employment, especially farm labor, such as harvesting
      crops seasonally; also called migrant laborer or
      migrant worker. Sometimes the migrant worker is not a
      resident of the country in which the work is performed.
      [PJC]

WordNet (r) 3.0 (2006):

migrant
    adj 1: habitually moving from place to place especially in
           search of seasonal work; "appalled by the social
           conditions of migrant life"; "migratory workers" [syn:
           migrant, migratory]
    n 1: traveler who moves from one region or country to another
         [syn: migrant, migrator]

Moby Thesaurus II by Grady Ward, 1.0:

127 Moby Thesaurus words for "migrant":
   DP, avifauna, baby bird, bird, bird of Jove, bird of Juno,
   bird of Minerva, bird of night, bird of passage, bird of prey,
   birdie, birdlife, birdy, blue-collar worker, breadwinner,
   cage bird, casual, casual laborer, chick, common laborer, cygnet,
   day laborer, displaced person, diving bird, dove, drifter,
   drifting, eagle, eaglet, emigrant, emigre, employee, evacue,
   evacuee, exile, expatriate, factory worker, fish-eating bird,
   fledgling, flightless bird, floating, flunky, fowl, free lance,
   free-lancer, fruit-eating bird, full-time worker, fulmar,
   game bird, gypsy, hand, immigrant, in-migrant, industrial worker,
   insect-eating bird, itinerant, jobber, jobholder, laborer,
   laboring man, menial, migrator, migratory, migratory bird,
   migratory worker, mobile, moiler, mover, navvy, nestling, nomad,
   nomadic, office temporary, oscine bird, out-migrant, owl,
   passerine bird, peacock, peafowl, peahen, perching bird,
   peregrinator, peripatetic, pigeon, proletarian, ratite, roustabout,
   rover, salaried worker, sea bird, seed-eating bird,
   self-employed person, servant, shore bird, songbird, squab,
   stateless person, stiff, storm petrel, stormy petrel, swan,
   temporary, toiler, transient, transmigratory, traveler, traveller,
   trekker, vagrant, wading bird, wage earner, wage slave, wageworker,
   wanderer, warbler, water bird, waterfowl, wayfarer, wetback,
   wildfowl, worker, workgirl, workhand, working girl, workingman,
   workingwoman, workman