Just personal opinions:
1. I would prefer to have the text box stay visible so I could go searching for another word without scrolling back to the top.
2. It'd be nice to have some management of the history list and bookmark even the basic ones.
3. Why is there a "pencil" on the right hand side of each searched words sometimes, what's that mean? I thought it's a button for what, but it's no function.
4. The flow seems a little odd. After lookup, click on the search box, it won't go back to the history list but a list of similar words. Button "back" will quit the App.
5. It'd be very useful if the search could be a segment that is not limited to the beginning of the words. I think it would be very handy function! Say, searching "and" could show me "handy" in the list of words found.
6. Lastly, I personal think the App icon could be a lot better.
Thanks for your great works!