The same argument could be presented for "magic" in a game.
I think that that is correct. I think that the word 'magic' is used in alot of ambigious ways and I think its pretty common to use it with little thought what it means. My favorite author (Tolkien, doh) lampshades this problem in LotR when he has Galadriel question Sam what he means by the word magic, since he seems to use it to describe things which are wildly different. At least however the notion of magic as it relates to fantasy is more clearly defined than psionics. I mean magic is generally the defining trait of fantasy, whereas its tangential to or non-existant in most fantasy stories. How am I to grasp what its percieved essential element is in a fantasy setting?
I suspect that under the surface, there isn't in fact alot of agreement at EnWorld on even the topic of magic. I can tell you exactly why Vancian magic works and why it has to work like that (for my campaign), but I know that there are alot of people at EnWorld that hate Vancian magic probably because they either can't concieve of how it works or else believe that magic simply shouldn't work like that.
For my part, I notice that the word magic is used variously to mean: 'things that I don't understand', 'things that don't happen', and 'these mechanical systems I've either experienced directly or else imagined based on reading some particular fiction'. Oftimes 'things I've imagined' in my opinion doesn't when extended out to its logical conclusion create the setting or story that inspired the imagination in the first place. And almost never do I see the word 'magic' used in the way that someone who believed in magic would use it. For example, I frequently see the claim that the cleric has no mythic basis but that the D&D wizard does - which is almost the opposite of my reading of myth and history. The Wizard strikes me as almost wholly modern, and the cleric as much closer to what premodern people thought of as 'magic'. And words like 'Sorcerer' (to say nothing of Thaumaturge) are used in wholly modern ways that have little to do with the origins of the term.
And by the exact same token, there are plenty of people with a very clear idea of what psionics means to them, despite your personal ambiguity.
Perhaps there are, but I'm still waiting to here clear descriptions of that. For example, based on my reading of 1e, psionics was 'Magic not tied to D&D's level system', which was frankly the only mechanical implementation of psionics that ever to me made the slightest sense. There was the quintessential elements of a wild sport with uncanny talent that you either had or lacked without control over it or the possibility of growth. There was a true differentiation from the oridinary magic of the system. Yet, praise for that core concept has been scarce in this thread, which makes me wonder what people would praise and why.