What is Atheism?

[Mister Agenda]

Yes.

It's called "understanding the null hypothesis".

That depends on what the null hypothesis actually is? The idea behind a 'null hypothesis' is that proving one explanation requires disproving the current explanation.

This is like one of those commercials where the person who actually understands something is saying 'That's not how any of this works1'.

If homeopathy was believed in for centuries and almost everyone but a few irrationally skeptical scientists believed in it unquestioningly, to prove it really works, the null hypothesis to overcome would still be 'homeopathically treated water is indistinguishable from the same water if not homeopathically treated in its medical effects'.

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Anyways, let's see how that applies to an alternative proposition. I think it would very disingenuous for nearly any atheist to say he or she disagrees with the claim "The world is all that exists" which is functionally equivalent to lack of belief in God.

'The world is all that exists' is the null hypothesis. If you want to show that something besides the world exists, that's the proposition that you need to overcome. It could well be true that the world isn't all that exists, but that's what needs to be demonstrated; it's nonsensical to hold the opposite as the null, because that's the opposite of what the null hypothesis is, and is for.

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Frankly, I preferred when the term "atheist" was more specific, and had more meaning.

Not sure how your preference is relevant, but that was literally centuries ago. And I think there may be a disconnect between 'word with multiple senses' having less meaning than 'word with just one'.

Faith has multiple senses. I'd be perfectly happy to pare it down to just one going forward, if you think it would make it more meaningful.