The Daily Grind: How would you define a sandbox MMO?

So yesterday on Twitter I conducted an extensive, exhaustive survey in which I asked, "Hai guyz, what makes a sandbox MMO a thing? You know?" It was probably a little less articulate than that. While I might be seen as the ultimate source of information in video games, the truth is that I'm struggling to come up with a precise definition of what, exactly, makes a "sandbox" MMO.

Interestingly enough, the responses that some friends sent back my way were as varied as could be, suggesting that this might be more of a murky area than I assumed. Considering how much we throw the term around, both on Massively and elsewhere, I think it might be beneficial to come to a consensus.

So how would you define a sandbox MMO? Is it the tools, the freedom, a lack of traditional leveling, the variety of non-combat activities, the tone, or something else entirely? Can you sum it up in one precise sentence?

Every morning, the Massively bloggers probe the minds of their readers with deep, thought-provoking questions about that most serious of topics: massively online gaming. We crave your opinions, so grab your caffeinated beverage of choice and chime in on today's Daily Grind!