I wanted to revisit the idea because it occurred to me that it's not just the term "God" that is meaningless but there are many other theological terms that are equally nonsensical or under-defined.
Take for instance "heaven" and "hell". I believe that the current definitions for the two are "spending eternity in God's presence" and "spending eternity separated from God" respectively. (YMMV, since some have an idea of heaven that includes pearly gates, fluffy clouds, and streets of gold while hell is either fire and brimstone or a cold grave.) Notice that both of definition are dependent on the concept of God, which we've already said is undefined.
Another fuzzy term is "sin". Sin is typically considered "an action or thought that goes against God's Will". But how can we know what is God's will if we don't even know who he is? At this point we are all just guessing about what he wants.
To give you an example of the effect all of these ill-defined terms have on theology discussions I will take a paragraph that I was recently able to provoke over at Yahoo Answers. God is now "Lof". Heaven is now "Nevel". Hell is now "Nimm". Sin is now "wub".
Nimm is a place of eternal separation from Lof, and people go there when they die because they chose to separate themselves from Lof while living on earth. Lof created us with a free will to make our own choices and separating ourselves from Lof is one of the choices we are free to make. Our free will is a wonderful gift from Lof in that he does not force us to love Him or to follow him. With out our free will, we would be nothing but puppets or robots, which does not please Lof, and certainly does nothing to better our lives. While Lof desires that everyone would choose to love him, many people will choose not to. These people will die in their wubs and be separated from Lof forever in hell. Man from the beginning has Lof’s law written in his heart, and has the power to obey it, and yet was capable of disobeying, being left to the freedom of his own will. Man was created with holy character prompting him to holy actions; but man was fallible, and did fall from his integrity. Many would say that this is unfair, and that a loving Lof would never set up a system such as this; it is precisely God’s love for us, and the fact that He is perfectly just, that tells why nimm exists, and why men and women will choose to go there. Lof loves us so much that He respects our freedom of choice. If we choose not to love Him, then why would He want us to live with Him eternally in Nevel? Wouldn’t living for eternity with someone we don’t love be a kind of nimm any way? Lof wants to spare those people who don’t love Him from having to live with Him and be under His rule for eternity.
Clear as mud, isn't it? I don't know how that could possibly make sense no matter what words you put in the place of God or hell. Add to it all of the mental wankery that is "free will" and that paragraph isn't even worth reading. This is why I see most of theology a waste of time. It's nonsense talk to give comfort to the ignorant masses.
I'll leave you with a real definition provided by Ambrose Bierce in The Devil's Dictionary:
Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel.