"Dictor" is offline dictionary app for playbook. It is native. But you need to get your favorite dictionary (stardict or unicode text format) first and copy them to playbook. Then you can import it and start query. More detail please have a look at the description in app world or send email for support.
I haven't found anything acceptable for an offline dictionary either. I was hoping that android functionality would bring a solution. I would pay for a proper app.
