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]