Dictionary.com
Free online English dictionary, thesaurus and reference guide, crossword puzzles and other word games, online translator and Word of the Day.
dictionary.com

The English - American Dictionary
A humo(u)rous resource for Americans learning British/Scottish English.
septicscompanion.com

Merriam-Webster's WordCentral.Com
Student dictionary and rhyming dictionary online at Merriam-Webster's website. Daily Buzzword by subscription.
wordcentral.com

Cambridge International Dictionaries
Search separate dictionaries of English, phrasal verbs, or idioms.
dictionary.cambridge.org

Chemistry Science Dictionary Englisch/Deutsch
Chemie Fachworterbuch Deutsch/Englisch - Englisch/Deutsch - Chemistry Science Dictionary German/English - English/German.
chemie.de

Dictionary.net
Comprehensive dictionary database of word and phrase definitions from 8 different sources.
dictionary.net

HyperDic
Based on the WordNet lexical database and thesaurus, covers a selection of the most frequent English words. Includes synonyms, antonyms, examples and pronunciation and more.
hyperdic.net

English Portal
Learn English online. Free exercises, idioms, common abbreviations, slang, proverbs and more.
english-portal.com

beetfoundation.com Dictionary and Thesaurus
General purpose online English language dictionary and Thesaurus.
beetfoundation.com

Bibliomania: Webster's Unabridged Dictionary of 1913
Forms version. Allows browsing headwords.
bibliomania.com

Wordsmyth
American English dictionary with an integrated thesaurus and other lexical resources.
wordsmyth.net

ARTFL Webster Search
American and French Research on the Treasury of the French Language Project - 1913 Webster's Revised Unabridged Dictionary. Simple Headword Search Script: 109,562 entries.
humanities.uchicago.edu

The Free Dictionary
Online dictionary for the English language and several other languages. Also, provides a thesaurus, acronyms and abbreviations, idioms, encyclopedia and a literature reference library.
thefreedictionary.com

Google Dictionary
English dictionary and online translator for words, phrases and websites in several languages.
google.com

Macmillan English Dictionary
Resource site for the new Macmillan English Dictionary.
macmillandictionary.com