many don't give a toss

Many words don't give a toss either, Bingley. But that's because they have no meaning, even as a misspelling. [Incidentally, a misspelled word like "inciteful" has meaning. It means "insightful". It's just that its proper spelling has been misplaced.]

We're using a lot of words to get at the meaning of a word which has no meaning.

What's wrong with tsuwm's solution: "word" and "non-word". Anything in between doesn't really exist because it doesn't mean anything to anyone.

So why not call a word which doesn't have any meaning to anyone, and has never had any meaning to anyone, a mu-word? Or, a "ghost word", as Maverick has suggested? Or why not just call it a non-word, or a non-existent word, and be done with it. :)

OK, I've got one if someone wants to give it a toss.

What do you call a cow that isn't a cow, doesn't look like a cow, has never been represented or acknowledged by anyone at any time as a cow, and has never existed or been misspelled as a cow?

Can anyone think of a word for it? And you can't say mu-cow 'cause that's too easy. :)