Source : Webster's Revised Unabridged Dictionary (1913)

Migratory \Mi"gra*to*ry\, a. [Cf. F. migratoire.]
   1. Removing regularly or occasionally from one region or
      climate to another; as, migratory birds.

   2. Hence, roving; wandering; nomad; as, migratory habits; a
      migratory life.

   {Migratory locust} (Zo["o]l.) See {Locust}.

   {Migratory thrush} (Zo["o]l.), the American robin. See
      {Robin}.

Source : WordNet®

migratory locust
     n : Old World locust that travels in vast swarms stripping large
         areas of vegetation [syn: {Locusta migratoria}]