One way to do it starting from a MOBI (book format) file is this:
1. explode the MOBI to HTML - eg by Calibre or mobi2html
2. look at the HTML file structure and write a script that turns it into a tab delimited file suitable for input to tab2opf.py
3. use tab2opf.py script to convert the tab delimited file to OPF+HTML(s) (with a different structure than the original HTML)
4. edit OPF file in an editor - metadata definition
5. write a script to add the inflections to the HTML file, the syntax is here:
http://www.mobileread.mobi/forums/sh...ad.php?t=59724
(the most complicated step if you want to catch vast majority of the inflected forms - plurals, diminutives, past tenses etc, different for every language)
6. use mobigen.exe to convert the prepared OPF+HTML to MOBI
By no means I claim this is the best, optimal or easiest solution - it is just what I did in order to use a Dutch-English dictionary with Kindle3. The existing scripts I mentioned above should be quite easy to find, download and use - clearly, except of points 2 and 5 where I have written my own scripts.
Note that you can probably skip the most complicated step 5 for the purpose you describe because the inflected forms are not caught by the typed search in the dictionary anyway. I included it only for the sake of completeness - if one wanted a way to convert a dictionary from a mobi book format into a "full" dictionary supporting complete instant lookup in books being read on the Kindle.