What is significantly more? Twice as many as normal? Ten times? What is an extreme price increase? Double? Ten times? Fifty times?
This all subjective and is no different than "you are saving more than I think you should, thus you are hoarding".
The problem with your logic is that the only person who can tell what is the correct amount of anything to save is that person, no one else.
There are different ways of measuring significance using statistics, but that does not mean it can not be done in a manner that does not rely on personal preference.
Also, I really didn't think there were any value judgments expressed in the definitions I offered. In popular discourse hoarding may have a negative connotation, but I thought you were looking for an economic definition that distinguished it from saving, which I think I provided.
With the exception of the crazy person, the definition I offered had nothing to do with personal preference. I could hoard guns and liquor and have no personal preference for these items, I could be someone who never drinks and never shoots.
The definition of hoarding simply refers to the acquisition based on an expectation of significant future price increases. Again, this is something that could be measured statistically, you could look at historical price variance for these assets, and if I was buying them with the expectation that their prices would increase beyond the normal distribution, I would probably be hoarding, regardless of my preference for the items.
With savings, on the other hand, there is no requirement that the saver expect that his savings will increase beyond the normal range of increase based on historical data and variance.