The Collaborative International Dictionary of English v.0.48:

Migrate \Mi"grate\, v. i. [imp. & p. p. Migrated; p. pr. & vb.
   n. Migrating.] [L. migratus, p. p. of migrare to migrate,
   transfer.]
   [1913 Webster]
   1. To remove from one country or region to another, with a
      view to residence; to change one's place of residence; to
      remove; as, the Moors who migrated from Africa into Spain;
      to migrate to the West.
      [1913 Webster]

   2. To pass periodically from one region or climate to another
      for feeding or breeding; -- said of certain birds, fishes,
      and quadrupeds.
      [1913 Webster]

WordNet (r) 3.0 (2006):

migrate
    v 1: move from one country or region to another and settle
         there; "Many Germans migrated to South America in the mid-
         19th century"; "This tribe transmigrated many times over
         the centuries" [syn: migrate, transmigrate]
    2: move periodically or seasonally; "birds migrate in the
       Winter"; "The workers migrate to where the crops need
       harvesting"

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "migrate":
   drift, emigrate, expatriate, flit, go, immigrate, in-migrate,
   intermigrate, move, nomadize, out-migrate, range, relocate,
   remigrate, resettle, roam, rove, run, settle, swarm, take wing,
   transmigrate, travel, trek, voyage, wander