Well then let's introduce two more terms and see if that helps any. "Religion" is a person's creative answers to questions involving God -- things beyond our ability to understand. That means when you look up into the night sky and say something like "Surely there is another intelligent civilization out there" you're being religious. Same goes for the early Greeks who thought the gods caused the rains. Such creative explanations are a natural part of humanity. We naturally try to affix order and creatively explain that which we do not know. In fact, exploratory science couldn't happen without it. I'm as religious as the next guy -- I have those creative explanations that I chose to incorporate in my life. But I try not to live in that world. And I try to actively understand when I'm being religious.
"Organized Religion" is really what probably gets your goat. You can thank the Catholic Church for that, which in the 3rd century took some religious letters and made them a Bible, hooked up with the largest world government at the time, and eliminated the competition. (I'm not bashing Catholics here. From what I know most seem like good people). As a monopoly, they controlled one version of "creative answers to things we don't know" for many centuries. To a large degree, even after the Reformation, the pieces of belief you see today in Christianity come from this long-lived monopoly.
The interesting thing here is that the tenets of some religion -- the set of creative stories commonly held -- and the actual practice of that religion by participants are two completely different things. So while Catholics, for instance, have this big set of beliefs, it's not unusual to see individual Catholics completely digress. Religion, for as much as people want to make it into a monopoly or a formal system of beliefs, is still actually practices in a very individual and creative way, just like it has been since the dawn of man.
What we're left with is the actual practice of religion is a deeply personal matter, and if you paint with a broad brush you miss the entire point of how religion actually works.
You're basically correct with your argument of "when I say believe in God, they're not going to think I mean X" but at the same time _you_ are the one who is missing the point in your imaginary conversation. If you ask somebody if they believe in God, the very next question from you should be something like "what does that mean to you?" because "believe in God" is nothing the same as "2 + 2 = 4" You're simply asking somebody if they have some belief in some "thing" that is out there beyond their understanding. What you really want to know is whether they conform to some organized religion that has these tenets that you find so despicable.
When you say "everyone else is using that definition", best I can figure you mean that in the western world, as part of your observations in English, the most vocal people use the term "God" as part of some discussion about their organized religious practices. I can buy that. But most people use the word "science" as something guys in white coats do, or the word "politics" to describe cheating weasels lying to each other, or the word "religion" to describe something that happens in a church.
People use all kinds of crappy terms. That doesn't mean that you get to pick and choose poorly defined terms and then go flailing away at them. It just confuses matters more. If you're going to slam somebody's belief system, don't go throwing a bunch of other people into the mix at the same time.
"Argh! Is there anyone on the planet who does believe we know everything? Please narrow your definition."
That has not been my experience. In another thread under this very article a commenter was making the assumption that modern-day morals can judge whether what some God figure does is right or wrong. I find that incredible, given our progression in what is right and wrong in the western world. It's common to see people act as if modern science understands 99% of everything, when most likely it's nowhere near that percentage. This attitude is taught in schools and, best I can tell, fits the definition of religious instruction. Science is a tentative set of rules that are interconnected and based on abduction, induction, and deduction. It's always tentative, but that part of science is uncomfortable for many, so we creatively explain how it's some sort of natural progression from ignorance to greatness. (In fact, as Kuhn noted, it goes in fits and starts, is highly political, and works from one paradigm to another) People who admire celebrities many times think they actually know all about the person from watching them on TV or reading their works, when in fact the public version of somebody and the private version are very different. Atheists will argue at length about there not being a God when, as demonstrated here, there's simply no way for anybody to know one way or another. Salesmen will think they know everything about what a potential client needs without ever talking to them.
Humans seem very good at thinking they know everything about a subject, whether it's science, religion, social interactions, whatever.
Epistemology -- the study of that which is knowable -- is a topic both for philosophy and religion. I wouldn't go separating the two, because there is and has always been heavy overlap. I'd argue the difference between philosophy and religion is minuscule.