For example, if a naturalist encounters a new species of wildlife, he/she then studies that species and comes up with a definition for it. No sane naturalist ever wakes up in the morning, invents a new species from imagination, and then goes looking for it. Instead, they explore with an open mind and simply accept the existence of whatever they find.
We must first observe, and then define, specifically in that order. It must be in that order because the definition needs to be based on what we observed. Attempting to perform this operation in reverse is called "making shit up."
Now this goes for both atheists and theists: When we talk about the existence of God, we keep getting this backwards.
Theists simply assert a definition of God at the start of an argument to prove his existence, which is circular. For example, the ontological argument basically states that God must exist by definition, according to a definition they just made up.
Atheists also confuse the issue, saying they "can't prove or disprove something until it has been clearly defined." That's true, but we're still approaching this backwards. You can't even define something until it has been observed. And if we could observe it, then we wouldn't need to prove or disprove it because it would already be proven by the fact that we just observed it. It's not so much that we can't disprove something that hasn't been defined; it's that we can't define something that hasn't been proven to exist in the first place. A definition must be based on what we observe about the thing that is being defined.
Confused? Let me simplify. Here's how to define God:
Step One: Find God.
Step Two: Observe God to determine his/her features, qualities, and behaviors.
Step Three: Define God based on the data you gathered in step two.
Currently we're at step zero. Good luck theists. Find me a god, whatever you think that is, and show it to me. Until then, I'm not interested in arguments about the definition of God. Sure, we can define a hypothetical God for the sake of discussion, or just for the hell of it, but please remember that doing so is nothing more than an exercise of the imagination.
[Feedback is appreciated. Please leave a comment below.]