The entire organization, including all of its subsidiaries. It implies a large corporation or government agency, but it may also refer to a company of any size with many systems and users to manage. It depends on context. A corner candy store is "someone's enterprise." The terms "enterprise," "company," "corporation" and "organization" are used synonymously.

Enterprise Class
When one hears about an "enterprise class device," it means high-end equipment typically for the large organization. See enterprise computing, enterprise architecture and enterprise networking.