The tech industry absolutely loves its buzzwords. Once a buzzword is born, it seems to take on a life of its own. Eventually it will be stretched to the point where its original meaning is almost completely lost. Look to "big data" or "cloud" for great examples of this. Sometimes it's helpful to take a step back and boil down the original phrase to its real meaning at a practical, technical level.
If VMware has its way (and it probably will), the next term in the IT lexicon to catch fire will be the software-defined data center (SDDC). SDDC has formed one of VMware's key talking points at this year's VMworld conference in San Francisco, and it is sure to lose its meaning as VMware's partners and competitors try to prove just how "software defined" they are.
How does one, er, define "software defined"? At first, you might imagine it refers to the abstraction of traditionally hardware-bound tasks into pure software solutions. That's often true, but it's too simplistic. Just because someone has implemented something in software without the aid of purpose-built hardware does not make it software defined. In fact, the use of purpose-built hardware doesn't preclude a solution from being software defined at all.
Instead, the true nature of software-defined anything -- whether it be storage, networking, or an entire data center infrastructure -- has much less to do with what hardware might be involved and much more to do with how it is managed and controlled.