Just to be different I'm going to talk about communication more than deities.
The act of defining a thing neither changes it nor brings it into existence. What it does is to bring into existence an appreciation which we can share, and which we can then refine and improve on or dismiss and replace.
If we don't define something - or can't - then our ability to share it is limited. All we can do is offer one another experiences which may or may not yield the same appreciations. But also, without definitions it's easy for us to get lost assembling experiences and trying to find meaning in them. Most of the development of human thought has been about discovering how to build good definitions and then work with them to improve our imperfect understanding.
But still there are plenty of appreciations that don't define well. Our art is full of them: love, beauty, honour, good. These concepts tend to be values-driven, experiential in nature and they change over time as our values change. These are interpretative, appreciative concepts. They're reflections of our spirits much more than reflections of the world itself, because the physical world does not change as fast as our appreciations of it do.
I personally believe that it's possible to produce functional
descriptions of love, beauty, honour and good. I just don't believe that they're true
definitions, in the sense of being prescriptive. They're more guideposts to experiences that allow (most) reasonable humans to discover something of value.
If you describe god (lower-case 'g') as something nebulous like a binding, connecting and abiding aesthetic in existence then it's something we can all talk about. Perhaps using different words - and using descriptions rather than definitions. Naturally our appreciations of that aesthetic will change as our values and experiences change. But it's possible to talk about that binding aesthetic with animist bushmen from Papua New Guinea, or a Hindu in Mumbai, or a Moroccan Muslim - because we are human and we value connectedness and beauty -- and our values aren't so different that we cannot understand one another with effort.
But if you start talking about God (capital G) as a personified, anthropomorphic image, then you're not talking about a sharable human aesthetic but a cultural myth that you've elevated to the personally sacred. That's okay, but in doing so, you've replaced a sharable, values-based human aesthetic with a prescriptive authoritarian symbol, so it's already lost some portability.
If you happen to be monotheistic then this can lead you into the mistaken idea that if your personal symbol has no currency to others, that it's somehow
their fault. Where monotheists have been responsible for the ill-treatment of others, they have always justified such ill-treatment under that one punitive judgement.
'god' (as I have described it) is not definable but you can point to it if you want, and people can accept it from their own, quite diverse perspectives and still share what they appreciate. The complementarity of those perspectives has its own value I think. If you want to increase your appreciation of red desert, you could do worse than to talk to an Australian aborigine.
'God' is much more definable because it's a cultural artifact. But good luck in getting everyone to accept your version of it.
I'm an atheist. I don't like 'God' because I consider its 'definitions' to be flawed. Unlike the concepts in science or philosophy, I don't believe that the definitions of 'God' are improving over time; I think that the pea of delusion is just being shuffled under different shells according to the mood of the times. But I can enjoy stars and harmony and human fellowship and honour and good and love just as much as the next guy. I can (and do) happily share my appreciations of that binding aesthetic with Christians and Jews and Muslims and agnostics and Hindus and the occasional animist from Vanuatu over a cup of kava. As I learn, I find myself agreeing with just about all of them on what kindness and love look like, and that the stars are very beautiful.
For me the hobby-horse of monotheism is an ugly, rotting creature, full of splinters and creaks with leering eyes and a mangy mane. As a child I had an eyeless teddybear worn thin with love, and I understand the sentimental attachment to such things. But just as nobody wanted to touch my drool-stained bear, so I don't like touching folks' 'definitions' of God. I just wish that the monotheists would realise that and go play by themselves.