Dictionaries and Thesauri

RefSeek's guide to the 30 best online dictionaries, thesauri, and definition aggregators. Listings are judged by authority, coverage, usability, and utility.

  • Abbreviations.com
    Directory and search engine for acronyms and abbreviations.
    abbreviations.com - AcronymsAlso see: Definitions.net
  • Acronym Finder
    Dictionary of acronyms and abbreviations. Contains over 750,000 definitions.
    acronymfinder.com - Acronyms
  • Answers.com
    Aggregator of definitions, encyclopedia entries, and language translations.
    reference.answers.com - Aggregator
  • Cambridge
    Search multiple dictionaries from Cambridge University Press.
    dictionary.cambridge.org
  • Computer Definitions
    Featuring 20,000 topics and 2,500 images. Search field at bottom of page.
    computerlanguage.com - Computers
  • Definitions.net
    Multilingual dictionary that provides definitions and translations.
    definitions.net - Aggregator - Also see: Synonyms.net
  • Dictionary.com
    Includes definitions from , Random House, and Merriam-Webster.
    dictionary.reference.com - Aggregator - Also see: Thesaurus.com
  • Investor Words
    Financial glossary with a comprehensive index of 7,500 definitions.
    investorwords.com - Financial
  • Law.com Dictionary
    Concise, easy-to-read definitions from The People's Law Dictionary.
    dictionary.law.com - Legal
  • Macmillan
    British English and American English dictionaries.
    macmillandictionary.com - Dictionary
  • MarketingPower Dictionary
    4,000 cross-referenced definitions of marketing terms.
    marketingpower.com - Marketing
  • Mathworld Dictionary
    Source of mathematical definitions and concept explanations.
    mathworld.wolfram.com - Math
  • Medi Lexicon
    Search over 200,000 medical terms, ICD-9 codes, hospitals, and more.
    medilexicon.com - Medical
  • Merriam Webster
    Based on the print version of Merriam-Webster's Collegiate Dictionary.
    m-w.com - Dictionary
  • Merriam Webster Visual Dictionary
    6,000 full-color images; 20,000 terms with contextual definitions.
    visual.merriam-webster.com - Dictionary
  • Net Lingo
    Definitions for thousands of terms in the field of technology and communication.
    netlingo.com - Technology
  • OneLook
    Meta-search tool indexing 13 million words from 1,000 dictionaries.
    onelook.com - Also see: OneLook Reverse Dictionary
  • Oxford Dictionaries Online
    Oxford's Compact English Dictionary contains 145,000 words and definitions.
    oxforddictionaries.com - Dictionary
  • Thesaurus.com
    Over 17,000 entries. Find synonyms, antonyms, and brief definitions.
    thesaurus.com - Thesaurus
  • The Free Dictionary
    General and subject dictionaries for financial, legal, and medical terms.
    thefreedictionary.com
  • Urban Dictionary
    Dictionary of contemporary American slang. Not appropriate for children.
    urbandictionary.com - Slang
  • Visual Thesaurus
    Displays a unique visualization of connections between words.
    visualthesaurus.com - Thesaurus
  • Vocabulary.com
    Outstanding dictionary and engaging vocabulary teaching tool.
    vocabulary.com - Dictionary
  • WebMD Medical Dictionary
    Thousands of medical entries from abdomen to zygote.
    dictionary.webmd.com - Medical
  • Webopedia
    Dictionary of computer and Internet terms.
    webopedia.com - Technology
  • Wiktionary
    Multilingual dictionary and thesaurus written and edited by the public.
    en.wiktionary.org - Dictionary
  • Word Spy
    Blog tracking new words and phrases in popular use.
    wordspy.com
  • Wordnik
    Aggregator of definitions, images, and word usage statistics.
    wordnik.com - Aggregator
  • YourDictionary
    Definitions, thesaurus entries, spelling, pronunciation, and etymology results.
    yourdictionary.com - Aggregator

Word Tools

  • Crossword Dictionary
    Find answers to crossword puzzles, anagrams and cryptograms.
    oneacross.com - Crosswords
  • Internet Anagram Server
    Remarkable, robust anagram lookup service from Wordsmith.
    wordsmith.org/anagram - Anagrams
  • RhymeZone
    Writing tool for poetry, song lyrics, greeting cards, and more.
    rhymezone.com - Rhymes
  • WordCount
    Artistic experiment that presents 86,800 English words, ranked in order of frequency.
    wordcount.org
  • Wordle
    Java-based word cloud generator. Customizable fonts, layouts, and color schemes.
    wordle.net - Collages
  • Write Rhymes
    Simple online notepad with rhyme suggestions for poets.
    writerhymes.com - Rhymes