Update Jun 6: Today I had cause to use this definition and I'm not sure, but my questioner (someone who's very well informed Semantics-wise) seemed slightly aghast at my brevity and simplicity. I understand completely. It's not a glowing definition, full of promise, imbued with excitement, and burgeoning with opportunity. That's a deliberate choice on my part. From what I can tell, fulsome descriptions haven't worked very well over the past few years partly because the technology hasn't been ready and partly because buyers like CIOs, CTOs, and IT managers of all kinds have heard such promises a million times before.
Inferencing/reasoning, SPARQL queries (even with public endpoints), and the flashy stuff that's so promising probably occurs on a daily basis in tightly controlled environments that engage in what I consider "exotic" research and are overseen by the most highly trained and sophisticated people in the world when it comes to this particular technology. That's a far cry from closing a million dollar (euro, yen, yuan, take your pick) sale for an enterprise application that will see widespread deployment to a relatively untrained audience.
When the Semantic Web evolves to the point where it can fulfill all the promises that people (me included) have invested in it, I'll change my definition. But for now, in terms of what I believe it can reliably do today, I'll define the technology as above, although I'll probably still refer to the future capabilities just to keep it interesting.
Besides, I truly believe the emphasis needs to be on the product (e.g. solution) and not its underlying technology. When Microsoft sells Word or Excel, it doesn't emphasize the use of C and Visual Basic (I admit there are exceptions to this) because that's not what people really care about. They want to be able to create documents and work with numbers. It's that simple.