Dictionary Search
Dictionary Search provides a very easy way to lookup (or translate) a word in a Web page or an email in an online dictionary such as thefreedictionary.com. Simply select the word you want to lookup. Then right click and select "Dictionary Search for ...". A new tab or browser window will open with the meaning of the word you selected. It works for both for Mozilla Firefox and Mozilla Thunderbird
Go to the installation page to install Dictionary Search.
If you like DictionarySearch you can consider making a donation.You can use up to 4 different dictionaries, which you can configure yourself. For more info go to the Dictionaries page. There you will find instructions on how to change or add dictionary. It also contains a large list of other possible dictionaries in a significant number of languages.
NOTE If you are looking for spelling dictionaries for thunderbird or mozilla mail you should visit http://dictionaries.mozdev.org
If you like to receive an email when a new version is released subscribe to the mailing list. (It's low traffic). Also if you have an idea for a nice feature you can send an email to the mailing list. Patches with improvements and translations are also highly appreciated.
Alternatives
Other related mozdev projects are Conquery, Dict and MyCroft.
