'Migration' definitions:

Definition of 'migration'

(from WordNet)
noun
The movement of persons from one country or locality to another
noun
A group of people migrating together (especially in some given time period)
noun
(chemistry) the nonrandom movement of an atom or radical from one place to another within a molecule
noun
The periodic passage of groups of animals (especially birds or fishes) from one region to another for feeding or breeding

Definition of 'Migration'

From: GCIDE
  • Migration \Mi*gra"tion\, n. [L. migratio: cf. F. migration.] The act of migrating. [1913 Webster]