@Jarrod1937Apr 21.2010 — #Not sure if the term has other uses elsewhere, but in general it means you're progressively adding features/fixes/improvements to a site. Meaning you're always improving it as time passes rather than the old, complete site redesign, paradigm.
@Jarrod1937Apr 21.2010 — #Apparently it does have another meaning. It basically is also a design paradigm, but instead focused on streamlining the site itself into its elements. For example, separating a webpage properly by its structural, design, and functionality items. This is achieved by using html with proper semantic markup, .css includes to then add the design/presentation layer, and .js includes for any client-side functionality.
The idea is that, instead of designing a site to work primarily with a set of requirements, the site is designed where it can be functional with just the base structural elements proposed in the html markup. It can then "progressively" add in other elements, if supported, to "enhance" the experience, like external .css and .js files.
I personally like the idea myself, and actually already attempt to follow such rules when possible... but in my opinion, with a lot of "web 2.0" technologies and sites, such a paradigm is not possible. What if a major site feature required javascript (bad practice, but it happens) or flash (like youtube). In those cases such a complete separation is not at all possible.