Here's one website you can use to translate words (English-French dictionary or French-English dictionary) : http://www.wordreference.com/

First, you can listen to the words with British and American pronunciations. And you can also have an English definition and some English synonyms. Let's take the example of the word "LOOK":

Then, this is 'LOOK' as a noun:

After that, you can have the translation of the word 'LOOK' as a transitive or intranstive verb :

Then, this is the word with different prepositions, such as LOOK AFTER, LOOK FORWARD, LOOK FOR... :

Finally, you can see the idioms, Oxford entries and the compound words:

'WORDREFERENCE' is a good dictionary. Much better than 'reverso' or 'translate-google'!!! Use it if you need a dictionary on the Internet!