iFinger is a handy search engine that uses the best dictionaries to give you definitions and synonyms for the words that you are looking up. This application works with dictionaries that are already downloaded on your computer so it can also work offline.
With iFinger you can choose from numerous dictionaries, written in various languages and download the ones that you need. Another good thing about this program is that can instantly display the Wikipedia results for your entries in the language of your choosing.
A real advantage for iFinger is that it can be instructed to automatically dock the title bar of your current active window. Furthermore, you can choose to place it anywhere on your screen and customize the color themes for the results.
While testing iFinger, I only found one obvious disadvantage. Although the program allows you to pin the definitions that it displays to any location on your desktop, you cannot customize their transparency level. This is bad as there will probably come a time when they will obstruct your vision over the text fragment that you are working on.
Personally, I think that IFinger is a handy tool that will surely help you out on many occasions.