Mac OS X Lion
Definition - What does Mac OS X Lion mean?
The opreating system is sometimes referred to as simply "Lion".
Techopedia explains Mac OS X Lion
Unlike previous operating systems, Apple did not include 10.7 on a disk. Lion has been designed to streamline some of the traditional Mac functions to make the OS more accessible. It also comes with a lot of integration to iOS and borrows certain features from iOS.
Apple boasted 250 new features for Lion when compared to Snow Leopard and many come straight from iOS. For instance, it comes with a feature called Launchpad that brings the iOS user interface into the Mac format. The apps can be viewed as if they were iOS apps on the desktop while the user shifts left and right through the pages they are segregated into. Lion's successor, Mountain Lion, further integrates the two operating systems.