The Free Dictionary

http://www.thefreedictionary.com/

This dictionary is very comprehensive particularly for complex expressions or idioms and available for free, but in return it is fraught with ads all over the result’s page. It's also interesting to highlight that, in addition to the general dictionary, you have access to specialized vocabulary in medical, legal and financial science along with a very useful dictionary of acronyms.

 


The dictionary

The Free Dictionary is a very comprehensive dictionary. The main source of The English dictionary is Houghton Mifflin's premier dictionary, the American Heritage® Dictionary of the English Language, Fourth Edition. This authoritative work is the largest of the American Heritage® dictionaries and contains over 200,000 boldface terms and more than 33,000 written examples. The Fourth Edition also incorporates more than 10,000 new words.

Containing 260,000 entries, the general dictionary is augmented with Collins English Dictionary – Complete and Unabridged, and is enhanced by 30,000 illustrations, an audio pronunciation feature, etymologies, abbreviations, biographical entries, and more. Definitions are accompanied by usage examples from classic works of literature.

Pronounciation
 

Thesaurus

A Thesaurus entry is often linked to a word entry in the dictionary. A picture related to the word semantics is often displayed.
Translations


Additionally, translations to Spanish, French, German, and Italian are provided by HarperCollins and feature contemporary vocabulary and expressions—including everyday terms

The idioms dictionary
 
relating to business, computing, current events, tourism and many other topics.

 

The idioms dictionary is compiled from the Cambridge International Dictionary of Idioms and the Cambridge Dictionary of American Idioms.