Online Dictionaries

English – English Dictionaries 

Macmillan Dictionary
Merriam-Webster
Dictionary.com
Answers.com
The Free Dictionary
Wiktionary (by Wikipedia)
Wordnik
Ask Oxford
Your Dictionary
Business Dictionary.com (business terms)
Medical Dictionary Online
Urban Dictionary (slang and idioms)
One Look – search engine that will look for definitions posted on other dictionary sites! Highly recommended!



English – French / French - English Dictionaries 

WordReference.com (also includes German, Spanish, Italian, etc..)
Grand Dictionnaire (business, technical, medical, scientific, etc..)
Sylang
Reverso
Larousse