Definitions of assimilation:

noun: in the theories of Jean Piaget: the application of a general schema to a particular instance
noun: a linguistic process by which a sound becomes similar to an adjacent sound
noun: the process of absorbing nutrients into the body after digestion
noun: the social process of absorbing one cultural group into harmony with another
noun: the state of being assimilated; people of different backgrounds come to see themselves as part of a larger national family
noun: the process of assimilating new ideas into an existing cognitive structure