The term "enterprise applications" usually applies to the data-driven software systems that big companies run their business with: payroll, personnel, inventory, purchasing, business rules, e-commerce, etc.
I work in a mega-company where any of the product line divisions would be a darned big company on its own. Plus we grow by mergers and acquisitions. This leads to a lot of independent and even duplicative systems. Enterprise to us means across the business silos or the whole company. It's very rare that every group will use some "enterprise" solution, but it's worth some effort when only a few do.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi