Loaded question, that is. That's like asking "what is time?" to a group of beginner physics students. It kind of lends itself to a lot of options, and none of them are necessarily right or wrong.
From a political standpoint, I would say that a good definition of freedom is that perfect balance between individual human rights, and respect for those rights in the instance others. To put it in more pragmatic terms, freedom would be having as many rights as possible without infringing on another person's rights in the process. You can read whatever book you like, but you can't physically harm another person, for instance. This becomes difficult, just because there are a lot of grey areas where these two elements conflict, like drinking and smoking. You can drink around pretty much anyone, but most places now force smokers to go outside. This is because of the indirect harm of second-hand smoking. However, someone could make the same argument that there is a similarly indirect harm inherent in the risk of an inebriated person driving a car and hitting someone. Maybe it's a little far-fetched, but it's an argument people make. That's what can make this kind of freedom a difficult thing to grapple.
(now, this is where I may get a little far-flung, bear with me, I'm an asian philosophy major and I promise I know, like, 85% of what I'm talking about)
Culturally, freedom is a very fluid thing. In western conventions, freedom centers primarily around individuality, and the freedom to do as you please. But in many eastern cultures, that individuality is of diminished importance in comparison to the whole. In those circles, freedom is more about a family's rights and restitution in the grand scheme of things. To give a few examples, a person from America might feel guilt over committing a crime against another person, worrying about the consequences to himself and how they effect him. Meanwhile, a person from China is far more likely to feel shame for betraying the respect and honor of his family, friends, and even ancestors. In the framework of freedom, then, a man concerned with his freedom in America might be thinking about his right to own a gun or to marry his same-sex partner, while a man in China or Japan might view the rights to family rituals being respected by the state as a more important freedom.
Philosophically, it entirely depends on what freedom you are speaking about, and from what perspective. In Buddhist traditions, total freedom is a lack of self stemming from spiritual enlightenment. In the Greek schools, true freedom was meeting death in the knowledge that betterment lies ahead beyond what we can achieve in this life. In African religions, freedom is the achievement of survival above all others that would wish your life theirs. To respect the world around you in as much capacity as is necessary to outsmart it. To Confucius, freedom was simply a byproduct of living a life in humility and pursuit of pure goals. To Nietzsche, freedom was mostly a cruel joke to all but those who already possessed it.
One thing is for sure, I find it highly unlikely that there could ever be one true concept of freedom. That would hardly be a very free way of thinking, would it?
(Also it's good to be back guys)