1- The Free Dictionary
This is my favourite web based dictionary. It supports several languages and it is also a thesaurus and offers acronyms, abbreviations, idioms, encyclopedia, search engine and literature reference library.
The world’s most popular free online dictionary with definitions, spell check, word origins, example sentences, audio pronunciations, Word of the Day and more!
Free online dictionary, thesaurus, spanish-english and medical dictionaries, audio pronunciations, Word of the Day, word games, and many more high-quality.
4- Visual.Merriam
This is a dictionary that catches the eye and enriches the mind with more than 20.000 terms with contextual definitions, 6000 full-color images of a wide variety of objects.
5- Visuwords
Visuwords™ online graphical dictionary — Look up words to find their meanings and associations with other words and concepts. Produce diagrams reminiscent of a neural net. Learn how words associate.
6- Webopedia
An online computer dictionary and internet search engine for internet terms and technical support.
7- Wordia
Wordia is a free games-based learning platform – built on the foundations of a dictionary – that blends word-based learning games with interactive video vocabulary.
8- Your Dictionary
The easy to understand dictionary with example sentences, famous quotes and audio pronunciations. Includes: thesaurus, business dictionary, computer
A collection of quotations about science by scientists and other writers both ancient and modern.
10- Online Etymology Dictionary
History and evolution of more than 30000 words, including slang and technical terms
11- One Look
Type in a word and search many dictionaries at once. Also has a reverse dictionary and translations.
12- NetLingo
NetLingo has thousands of definitions that explain the online world of business, technology, and communication including the largest collection of Internet acronyms and text messaging shorthand
13- Music Dictionary
As its name indicates, this is a dictionary for musical terms
14- Medical Dictionary
The Medical Dictionary provides explanations of various medical terms and diseases.
15- Internet Picture Dictionary
Free, online multilingual picture dictionary with interactive activities for English, French, German, Spanish, Italian and ESL learners.