I have a really fast dictionary application (with nearly O(1) complexity of the search which means it does not depends on the size of the dictionary), so I found that database cannot provide satisfactory speed, but a file with thoroughly designed indexing can.
Please my past answers on the problem:
what is the best way to create a dictionary application
Is there any English dictionary including pronunciations?
Dictionary in android as app with eclipse
I use this application by myself and I would not mind to share this code, but unfortunately it is far from being ready for that. I though that some ideas and some information on my experience could be useful for you.