How does one define Leadership?

I know that as you are reading this post the first thought that's coming to your mind is not another blogger pontificating about leadership. However, being a pragmatist (OK, maybe a pessimist or a realist) I find myself fascinated by the multitude of definitions and so called theories that are out there which describe "Leadership". My goal is to simply provide my rudimentary view and explore the perspectives of others as I swim through these murky waters. 

So, my question is: "how does one define leadership?" Seems like a simple question, but is it really? Considering that there are so many books, blogs, articles, people, etc... that claim to have leadership defined how do you know which is correct or which one you should prescribe to?

My feeling is there isn't one. There is such an overabundance of definitions / theories that it speaks directly to the very human element of leadership, thus leading to the complexities of its practices and a common definition. It is as varied as there are leaders and those that crave leadership.

We can certainly categorize the attributes that we feel comprise a great leader (i.e. visionary, motivator, positive, etc...) and the different styles or types of leadership (i.e. transformational, enforcer, serial entrepreneur, etc...), but at the end of the day isn't it simply one thing: "Leadership is calculated guidance".

Thoughts?