Maybe, but no one has done it. It would involve writing a custom ACX.
On my Kindle Touch, I can search the dictionary directly from the top navigation bar. It has a scope for searching the book, all books on device, the dictionary, Wikipedia, or the Kindle Store.
Alternatively, find a third-party dictionary that has more inflections and stuff. Or (mentioned for the sake of completeness) write your own if you have the spare time, there are guides here on compiling your own dictionary.
Just because the Kindle comes with pretty good free dictionaries, doesn't mean you aren't allowed to look for more options.
