Vocabla for Firefox can translate English words using double-click. This plugin translates words from English to Spanish, Polish, and English definitions. You read and find new English word, double Click on it, and you get Translation.
Full Specifications
What's new in version 1.5
General
ReleaseApril 25, 2013
Date AddedApril 26, 2013
Version1.5
Operating Systems
Operating SystemsWindows 2003, Windows Vista, Windows, Windows 7, Windows XP