An ouster is the act of forcing someone out of a position, job, or place they occupy. When a company's board of directors removes a CEO who isn't performing well, that's an ouster. When citizens vote a mayor out of office, that's an ouster too.

The word carries a sense of forceful removal by those with authority. If a principal resigns on her own, that's not an ouster. But if the school board removes her against her will, that is an ouster. The person being ousted typically doesn't want to leave and may resist, but someone with authority makes it happen anyway.

You'll often see this word in news about business or politics. A company might announce the ouster of its president after a scandal. A country might experience the ouster of a leader through elections or, in more dramatic cases, through a revolution.

When someone faces an ouster, it's usually a significant event with real consequences, not a routine change of personnel.