In a couple of ways.
First, a God is anything or anyone that's been deified. That is to say, when a person or group, with serious conviction, say that a thing or person is a God, or whatever word is conceptually equivalent in their given language (assuming one exists, of course), then that thing or person is a God for those people. In this sense, "God" is a title (akin to terms like "King" or "janitor"), and the status of Godhood is subjective, sourced in external application, and independent of any intrinsic qualities. Emperor Akihiko, for example, is a God by virtue of Shinto, but he has no superhuman/supernatural qualities. The same was true of the Pharaohs, and of Caesar.
Second, a God is a term that illustrates the relationship between worshiper and worshiped. For example, to me, Earth is a Goddess, but that does not necessarily mean that I believe She has a conscious mind or self-awareness (independent of us, that is), or even necessarily "life" in a scientific sense. When it comes to Earth's intrinsic qualities, I do not, and will never, go against what the scientific consensuses are about Her. But while She is not a Goddess for everyone, She is a Goddess for me, because that's how I relate to Her, regardless of whether She is scientifically "alive" or not.