Microsoft has a good explanation about what an "enteprise application" is:
An enterprise application is a business application, obviously. As most people use the term, it is a big business application. In today’s corporate environment, enterprise applications are complex, scalable, distributed, component-based, and mission-critical. They may be deployed on a variety of platforms across corporate networks, intranets, or the Internet. They are data-centric, user-friendly, and must meet stringent requirements for security, administration, and maintenance. In short, they are highly complex systems.
Microsoft has a good explanation about what an "enteprise application" is:
from msdn.microsoft.com/en-us/library/a...
Checkout their Enterprise Application Requirements
Basically the difference is the scope.
My understanding is that it's not always black and white though.
From the definition and my experience, I can just know that enterprise application is a business application which is very complex in all aspects.