WBabylon

WBabylon is a bidirectional translator / dictionary which translates between Japanese and English running on Windows. After selecting a word on the screen, a pop-up window will appear to show you translations. The translation is bi-directional, English to Japanese and Japanese to English. It is a free/open-source application. Wbabylon translates a word stored in the system clipboard. So after selecting one, pushing Control-C and then pushing one of hot keys. The hot keys are "F8" for Japanese words, "F9" for English words.

Requirements:

Microsoft .NET Framework 3.5