Are 'X exists' and 'X is real' only different ways of saying the same thing or are they different?
I'm leaning towards the former.
We might say a virtual reality world, seen while wearing goggles or a helmet or whatever, "exists" but isn't real. If it both doesn't exist and isn't real, then how would we be seeing it?
Or do goggles, computer programming, and electricty comprise the existence of something that isn't real?
Indeed even if the universe is illusory (not unnecessarily simulated but that is included under this umbrella term) we can still learn "facts" about how our "universe" works and interact with it reliably. The question is ultimately less important than we make it out to be. It is important however to accept human epistemology and it is impossible to prove a negative. There can never be any evidence for something that does not exist. I tend to accept reality provisionally and provided we accept reality we can also provisionally accept the findings of modern science until such time as we know more (and of course the human experience continues to evolve and as we come to understand our "universe" better).
I don't think you can do philosophy with a dictionary.
It is not a "word game" to clearly define your terms and/or define the context they are to be used.
But suppose we want to discover the nature of truth, or of morality. One cannot 'clearly define' what is unknown.
Or perhaps we dispute the nature of morality - whose definition do we use then?
And if we use two definitions of morality, are we talking about the same thing each time?
'Morality' is a word in the English language, so dictionary compilers are obliged to put something in their books but working out what morality truly is the job of philosophers, not dictionary writers.
An alternative approach is provided by Wittgenstein who summed it up as "Meaning is use". By attending to the ordinary language contexts that give words their meaning, we can avoid misusing them and trying to make them mean things that they aren’t made to mean. That's the theory, anyway!
As I understand it, the idea is to examine words in the context of ordinary discourse rather than imposing a definition from the outset. Of course the discourse has to be intelligible and coherent - word salad is not 'discourse'.
Wittgenstein argued that we do not learn the meaning of words as definitions; we pick up on the rules for using a word in discourse. Therefore philosphy is - or it should be? - concerned with a word's usage, not its dictionary definition.