For my work, Enterprise had a few key characteristics:
A separation of chooser and user. Often the systems were procured by IT departments, provisioned and deployed (I’m using their terms on purpose). They did not often prioritize the UX, so UX often suffered in favor of systemic value to the organization. When they came to me at IDEO, they were trying to catch up on UX and improve this systemic value. The systems that nurses, stock traders, and lawyers use are great examples.
Business-business, often the interfaces were distinctly not consumer. They were to help people improve the way they ply their trade. Typically the offering was from one business to another, not something people would chose to play with on a weekend, nor use, if not compensated for it.
A professional user. Often the tasks, goals, are professional in nature. Often the complexity is such that a naïve user could not understand the system nor make use of it. They are tools, often esoteric, requiring 5-10 years of experience in the field to make good use of. My earlier example of “brand-category manager” is one such. Sales or relationship-manager is a more accessible tool. The latter, is an example of a sophisticated tool I designed for a large financial client - one that I wish I could use today - it would be extremely useful in this highly-networked world. There is a need for more sophisticated tools today for everyday.