Term for when a big company buys out a smaller one?

The term for when a big company buys out a smaller one is called an "acquisition." In this process, the larger company purchases a majority stake or the entire ownership of the smaller company. Acquisitions are often pursued to expand market reach, gain new technologies, or increase competitive advantage. If the acquisition is friendly, it typically involves mutual agreement; if hostile, it may occur against the wishes of the smaller company's management.