The American Heritage Dictionary of the English Language
Encarta World English Dictionary
Longman Dictionary of American English
Longman Language Activator
Oxford ESL Dictionary : for Students of American English
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
Merriam-Webster's Collegiate Dictionary
NTC's American English Learner's Dictionary
Practical English Usage
Random House Webster's College Thesaurus
A multi-source dictionary search service, it searches for definitions in a number of different Webster's and American Heritage dictionaries. The source of each entry is given immediately after the entry.
Longman Dictionary of Contemporary English Online
Includes pronunciation for most words, examples, and a link to a verb conjugation table for each word. One of the best free online dictionaries for ESL learners.
Includes an online dictionary, thesaurus, audio pronunciations, Word of the Day, word games and other English language resources.
NetLingo Internet Dictionary
Comprehensive dictionary and glossary of Internet acronyms and jargon used in e-mails and chats.
Newbury House Dictionary of American English
Contains over 40,000 entries. Includes simple, clear definitions, sample sentences and idioms, activities and a pronunciation guide.
Wordsmyth English Dictionary-Thesaurus
Defines words and suggests synonyms.