[Numinous]

I notice that Amazon is selling Merriam-Webster's Collegiate Dictionary, 11th Edition which is the dictionary I normally use at home in both the dead-tree and computer versions. Apparently, though, if I buy it I can't use it as the default dictionary for the Kindle look up feature.
Which dictionaries can be used? is there a version of MWCD that can be used? Where could that be found and what would be necessary to make it usable on the Kindle?
Ok, I'm a hopeless noob.
Numi