Word Reference Translator од spassaro

Features:

• Translate a word by:
  
  • Double clicking it and then clicking on the floating link.
  • Selecting the text to translate and using the context menu.
  • Pressing the "T" key having selected text (configurable and requires permission on the site for pop ups).
  
  
• Support for the following languages:
  
  • English
  • Spanish
  • French
  • Portuguese
  • Italian
  • German
• Settings page accessible from context menu and add-ons list.

Disclaimer:
If a word being translated to a certain language belongs to that language already, WordReference site takes you the inverse translation. For example, if settings are to translate from French to English but you choose to translate the word "suck", WordReference will take you to the translation of "suck" from English to French.
This behavior is inherent to the site and has nothing to do with the add-on.