Westernization refers to the process by which the western culture is assimilated and absorbed into another culture. It is the social process in which the customs and practices of the so called western civilization becomes the order of the day in a different culture.
It is the process of absorbing one cultural group into another and assimilating it in away that they, to some extend show your culture and practices in them. Westernization is also called occidentalisation i.e. a process by which societies adopt the Western culture in such matters as technology, industry, politics, lifestyle, economics, language, law, diet, philosophy, religion ...