Top Online Dictionaries to perfect your Vocabulary

A dictionary is a book of alphabetically listed words in a specific language, with definitions, etymologies, pronunciations, and other information;[1] or a book of alphabetically listed words in one language with their equivalents in another, also known as a lexicon.

Acronym Finder
With more than 600,000 human-edited definitions, Acronym Finder is the world's largest and most comprehensive dictionary of acronyms, abbreviations, and initialisms. Combined with the Acronym Attic, Acronym Finder contains more than 4 million acronyms and abbreviations.

The American Heritage® Dictionary of the English Language
Over 90,000 entries feature 10,000 new words and senses, 70,000 audio word pronunciations, 900 full-page color illustrations, language notes and word-root appendixes.

BNC
The British National Corpus (BNC) is a 100 million word collection of samples of written and spoken language from a wide range of sources, designed to represent a wide cross-section of current British English, both spoken and written.

Dictionary - MSN Encarta
Search terms and find Dictionary definitions or find synonyms and antonyms.

Lexicool.com online Dictionary
The directory currently has links to over 6000 dictionaries and glossaries, many of which have been created by translators working in very specialist fields.

Roget’s II: The New Thesaurus
Containing 35,000 synonyms and over 250,000 cross-references in an easy-to-use format, this thesaurus features succinct word definitions and an innovative hyperlinked category index.

Dictionary.com
Dictionary.com is a multi-source dictionary search service produced by Lexico Publishing Group, LLC, a leading provider of language reference products and services on the Internet. To use the dictionary, simply type a word in the blue search box that appears at the top of every page and then click the 'Search' button.

YourDictionary
The free dictionary search gives you definitions, thesaurus entries, spelling, pronunciation, and etymology results for your word. Alternatively, you can browse the English dictionary alphabetically or by related terms to find meanings and synonyms. In addition, YourDictionary provides resources to help you find the best dictionary and translation sites for French, Spanish, Italian, German and hundreds of other languages.

OneLook Dictionary
12,739,111 words in 1065 dictionaries indexed, a OneLook Dictionary Search Engine

Cambridge Dictionaries Online
Publish dictionaries for people learning English all over the world.

Free English Online Dictionary
Roughly 6,912 known languages and dialects spoken in the 191 countries of the world, only 2,287 have writing systems (the others are only spoken) and about 300 of these have online dictionaries. You can search for them on Google and wade through 50 million mostly irrelevant returns or quickly peruse the cream of the crop here at alphaDictionary. We carefully select and add new dictionaries, grammars, and LANGUAGES regularly