a large company that controls all or most of a particular business activity
Judge Jackson's ruling that Microsoft is a monopoly has had only a limited effect on its share price, as most analysts were expecting this ruling.
complete control over a particular area of business or political activity so that other organisations cannot compete
The Systembolaget has a monopoly on the sale of alcohol in Sweden.
something that only one thing, person, or group has
I have no monopoly of wisdom.