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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.


Directory and search engine for acronyms and abbreviations.

abbreviations.com - Acronyms - Also see: Definitions.net

Acronym Finder

Dictionary of acronyms and abbreviations. Contains over 750,000 definitions.

acronymfinder.com - Acronyms


Aggregator of definitions, encyclopedia entries, and language translations.

reference.answers.com - Aggregator


Search multiple dictionaries from Cambridge University Press.


Computer Definitions

Featuring 20,000 topics and 2,500 images. Search field at bottom of page.

computerlanguage.com - Computers


Multilingual dictionary that provides definitions and translations.

definitions.net - Aggregator - Also see: Synonyms.net


Includes definitions from American Heritage, 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


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


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


Over 17,000 entries. Find synonyms, antonyms, and brief definitions.

http://thesaurus.com/ - Thesaurus

The Free Dictionary

General and subject dictionaries for financial, legal, and medical terms.


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


Outstanding dictionary and engaging vocabulary teaching tool.

vocabulary.com - Dictionary, Learning

WebMD Medical Dictionary

Thousands of medical entries from abdomen to zygote.

dictionary.webmd.com - Medical


Dictionary of computer and Internet terms.

webopedia.com - Technology


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.



Aggregator of definitions, images, and word usage statistics.

wordnik.com - Aggregator


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


Writing tool for poetry, song lyrics, greeting cards, and more.

rhymezone.com - Rhymes


Artistic experiment that presents 86,800 English words, ranked in order of frequency.



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