Lookwayup.com is an online dictionary which is free for light users (less than 10 uses a day) and paid for heavy users.
The system can be embded into your webapges aswell as used dircetly form this site as a regular online dictionary installed into your browser. Another cool thing about this site is that they support many languages: English, Spanish, French, Portuguese, German and Dutch. Also there’s the option of translating words from one language to another. But the site is not intended for doing full translartions, it just works for words The site is easy to use, and supports an amazing amount of words. Therefore you can be sure that no matter which word it is that you are looking for, the site’ll most surely have it. If this is not enough for you, since the translation options are very limited, or perhaps you don’t understand a definition, you can use the thesaurus application that’ll certainly get you out of any doubts. 
