I have no need to define it personally. I'm just curious how others define it. But I see now that many folks can't do that.
Closest I can think of is by literal definition, one reality. Think of being in a blackened room with five people of different Christian denominations (so five different perspectives). No one knows what the room looks like (or knows "everything" about life-all is a mystery since we can't see). One person says reality (the walls of the room) is the color green. One says red. One says yellow. There is only one reality-one life-one room (no Absolute and no Caps just as is). Denominations try to "design" the room and assume that life and reality is how they themselves define it. Some people who aren't religious are indifferent to life or reality. We live and let live and follow our values and live the best we can until we die (cliffnote version). We accept things as is. While others need to paint a picture of the walls in the darkened room to live best in it.
The Truth is the room that they are in (one life in which we all live-plants, animals, humans, and the existence and movement of energy as the physical universe. As well as one life in which all inanimate things exist). God is seen as the "Mystery" of reality (the questions we can't answer-the purpose/the inner goal/the experience of the present moment/or the hope for a future heaven.
What cannot be named (per hence the word mystery). It just is.
That's what truth means. One life. One reality in which all are apart because everyone and everything is made up of energy; and, that energy pervades everything because it is everything.
The problem is trying to own this truth-this mystery. Each person decides to put adjectives to their perspective of life itself (as above) and they decide that their experiences whether mystical or not are the cornerstone(s) of gratitude, love, and being one with life itself.
I think maybe you're focused more on how people described the colors and assuming that's what they mean by truth. But it isn't an ownership thing. Just one life-one reality-one energy.
Simple word is life and energy. Whether it's physics, something you experience, something that is, or something that people feel runs through them, that's pretty much the same life.
But I would not call it god (or any name). Like they say. Language doesn't quite encapsulate mystery. By definition. Not everyone capitalize mystery but many religions learn how to live life and understand life and interpret life and mystery thereof. (That's truth-understanding of it, living it, or being awed by it)