davidmich, you’ve asked a form of this question before. The answer is the same:
Deflation as the word is typically used is just negative inflation. It’s when the general price level is dropping instead of rising. To say it again: There is no dispute here. The correct definition is the one professionals actually use around the world.
There are some ignorant people out in the world who are in denial about this. They are best ignored, but since a sufficient number of them infest the internet, they can sometimes poison discussions with their nonsense, and you might be curious where this stupendous error comes from.
In the past, inflation was defined as an increase in the supply of money. People had noted the relationship between more money and an increase in the price level, and so people spoke of an inflated supply of money driving the process. (This meant that in the past, “deflation” was a decrease in the supply of money.) Over time, people realized that that there were many possible definitions of “money”, and that the price level did not perfectly correlate with the increase in any of them, at least not over the short term. The Quantity Theory of money is a highly imperfect way to study prices over short time periods, and prices are what we care more directly about. Because money can be so hard to define, economists started focusing on changes in prices. Because prices get much more attention, it didn’t take long for the term “inflation” to be shifted to changes in the price level. (This means that “deflation” is a decrease in the general price level. Deflation is just negative inflation.)
This shift in meaning is complete now. Deflation is negative inflation. Deflation is a general decrease in the price level. This is the meaning that professionals worldwide use. If you use an out-of-date definition, you will exclude yourself from that conversation.
You keep running into silly alternate definitions because ignorant people tend to fall into the etymological fallacy. They believe that since the word “inflation” (and therefore “deflation”) meant something different in the decades before they were born, it should still hold that meaning today. Call it a form of economic prescriptivism. Like the majority of prescriptivists, they are simply wrong.
A domain name doesn’t mean anything. Anybody can get a domain.
In one of the other cites you strangely provided, you’ve quoted some idiot who wrote into a newspaper. And that’s not my personal evaluation. Even the columnist said the guy’s ideas were “idiotic”.
Nothing has changed from the last time you asked this question about inflation. Deflation is just the other side of the coin. The definition is crystal clear. Deflation is a drop in the general price level. Anyone who says different would rather muddy the discussion than communicate clearly.