Control-command-D and Dictionary.app discrepancy

Question

I often use control-command-D with Safari to get definitions of words I find on web pages. I always thought that the dictionary used by control-command-D was the same one used by Dictionary.app.
But increasingly I am finding words that are in Dictionary.app aren't in the dictionary used by control-command-D (see the screen shot below), so I guess there is more than one dictionary. Can anyone point me to where in OS X the dictionary file for control-command-D resides? Is there any way to make it consistent with the one used by Dictionary.app? Thanks.

Answer 1

It's either a defined subset of the dictionary used in Dictionary.app or an entirely different dictionary. I'd like to know which one it is if possible, and where in the system it is stored.
More words in Dictionary.app but missing from command-control-D, from the same Wikipedia page,
are infallibility, inherently, and nonexistence. Interestingly, Gnosticism has a command-control-D definition, while Agnosticism does not, despite both having an entry in Dictionary.app.
Even more interesting: Typing nonexistence in the field right now resulted in Safari underlining it as a misspelling. Safari didn't do that for infallibility or inherently. Same thing in TextEdit - nonexistence was underlined; inherently was not. So that suggests a third dictionary or third defined subset - the one used by applications for spell checking.
This is getting stranger all the time...