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 - Acronyms
  • Acronym Finder
    Provides definitions for more than five million acronyms and abbreivations.
    acronymfinder.com - Acronyms
  • Cambridge
    Search multiple dictionaries from Cambridge University Press.
  • Computer Language
    Dictionary and encyclopedia including 25,000 entries and 6,000 images.
    computerlanguage.com - Computers
  • Definitions.net
    Aggregates definitions from multiple respected dictionaries.
    definitions.net - Aggregator - Also see: Synonyms.net
  • Dictionary.com
    Includes definitions from American Heritage, Random House, and Merriam-Webster.
    dictionary.com - Aggregator - Also see: Thesaurus.com
  • Law.com Dictionary
    Concise, easy-to-understand definitions from The People's Law Dictionary.
    dictionary.law.com - Legal
  • Lexico (by Oxford)
    English and Spanish dictionary and thesaurus from Oxford University Press.
    lexico.com - Dictionary
  • Macmillan
    British and American English dictionary and thesaurus.
    macmillandictionary.com - Dictionary
  • MathWorld Dictionary
    Source of mathematical definitions and concept explanations.
    mathworld.wolfram.com - Math
  • Merriam Webster
    Based on the print version of Merriam-Webster's Collegiate Dictionary.
    merriam-webster.com - Dictionary
  • Merriam Webster Visual Dictionary
    6,000 full-color illustrations; 20,000 terms with contextual definitions.
    visualdictionaryonline.com - Dictionary
  • Net Lingo
    Definitions for thousands of terms in the field of technology and communication.
    netlingo.com - Technology
  • Online Etymology Dictionary
    Explanations of what our words meant and how they sounded hundreds of years ago.
  • OpenMD Medical Dictionary
    Aggregator of medical definitions for 10,000+ medical concepts with images and pronunciations.
    openmd.com - Also see: Medical Abbreviations
  • The Free Dictionary
    General and subject dictionaries for financial, legal, and medical terms.
  • Thesaurus.com
    Over 17,000 entries. Find synonyms, antonyms, and definitions.
    thesaurus.com - Thesaurus
  • 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
  • Webopedia
    Easy-to-understand definitions for thousands of technology terms and acronyms.
    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.
  • Wordflex (Oxford)
    Builds dynamic trees that are filled with synonyms, antonyms, syntactical associations.
    wordflex.com - iPad Only
  • Wordnik
    Aggregator of definitions, images, and word usage statistics.
    wordnik.com - Aggregator
  • Wordsmyth
    Dictionaries, word tools, and an amazing illustrated dictionary for children.
    wordsmyth.net - Also see: Illustrated Dictionary for Kids
  • 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
  • Google Trends
    Explore and compare the popularity of words over time and geography based on Google search data.
  • Internet Anagram Server
    Remarkable, robust anagram lookup service from Wordsmith.
    wordsmith.org - Anagrams
  • Rhyme Desk
    Excellent rhyming dictionary with phonetic word search, thesaurus, and near rhymes.
  • RhymeZone
    Writing tool for poetry, song lyrics, greeting cards, and more.
    rhymezone.com - Rhymes
  • Write Rhymes
    Simple online notepad with rhyme suggestions for poets.
    writerhymes.com - Rhymes