Oxford Learner’s Dictionary http: //www.oxforddictionaries.com/
Free online Dictionaries http: //www.thefreedictionary.com/
Cambridge Dictionaries Online http://www.cambridgedictionary.org/
The free dictionary http://www.thefreedictionary.com/
Collins dictionary http://www.collinsdictionary.com/
Merriam Webster dictionary http://www.merriam-webster.com/
Macmillan dictionary http://www.macmillandictionary.com/
dictionary.com http://www.dictionary.com/
Acronym Finder http://www.acronymfinder.com/
definitions.net http://www.definitions.net/
vocabulary.com https://www.vocabulary.com/
Medical dictionary http://dictionary.webmd.com/
Law Dictionary http://dictionary.law.com/
Reference.com https://www.reference.com/
Foldoc online computing dictionary http://foldoc.org/