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"