Webster's Online Dictionary and Multilingual Thesaurus
Webster's Online Dictionary has the avowed goal of creating the largest online dictionary in the world, available currently in 90 modern and 10 ancestral languages. Part of its source material is also based on the 1913 Webster's Dictionary. They do not worry whether a word is slang or profanity, but do define it as such.
It is certainly the most comprehensive of all the free dictionaries online. It includes the definitions for a word, the date the word was first used in popular English literature, the etymology of the word in several languages, if relevant, including the word in different root languages and specialty definitions of the word in various domains. It has additional specialty definitions of the word with context, and the word used as part of a phrase in different disciplines. It offers Abbreviations, Acronyms, Synonyms, Synonyms within context, as in a thesaurus, and a section on crosswords, where it gives words which may be used with the definition of the word you are defining. It gives the languages where the same word is used, and the meaning of the word in that language.
There is a section on modern usage, with the word used in screenplays, lyrics, and movie titles. There is a section on commercial usage, with a link to the commercial site. It also gives images of the word in photos, illustrations, and digital media, and sound files captioned with the word. There are also sections on the use of the word in both fiction and non fiction usage, spoken usage, and speeches. As well, the usage frequency of the word in the English language is provided, along with the part of speech most often used, and the percentages of other parts of speech in which the word is used. It provides expressions where the word is used and the frequency of Internet keywords using the word daily.
Modern translations of the word are provided in 40 different languages in the word I researched, along with alternative meanings in that language, as well as ancestral language translations for the word. It gives a Bible trace for the word, with the source and the word in the original edition of the Bible, and the same Bible verse given in a number of other languages. There are derivations and misspellings, along with most of the common misspellings which bring you the word as a choice in a spellchecker. There are words which rhyme with the word you selected, and anagrams using the letters in the word.
At the end, there are sections with the word used in titles for literature, art, professional photos, proper noun and Trade noun usage, music, videos, and products. These last sections all contain links to where you can purchase the products, and affiliate income from these purchases help maintain the site.
Finally, it gives a Google search box with the word, and an index with links to all the sections in the word definition in the Webster's Online Dictionary.
It has instructions for putting on a search box for the dictionary on your own web site.
The Online Dictionary is based on Webster's Dictionary- 1913 Edition; this is a copyright free edition of the Webster's Revised Unabridged Dictionary Version published 1913 by the C. & G. Merriam Co. Springfield, Mass. It also contains material from WordNet 2.0 Copyright © 2003 by Princeton University. All rights reserved. It has a Legal Dictionary in the Public Domain, material from The Free On-line Dictionary of Computing (http://www.foldoc.org/), Copyright Denis Howe, distributed under the terms of GNU General Public License, a list of Acronyms: Acronyms This is a special GNU edition of V.E.R.A., a list dealing with computational acronyms. Copyright (C) 1993/2002 Oliver Heidelbach. It is released under the GNU Free Documentation License. As well, there is a Dream dictionary, with content provided by http://www.spiritualplatform.org/ and http://crackwalker.ca
As you can see from the image above, the Online Dictionary has gone with a very minimalist approach to their dictionary interface.
When you enter a word, it gives you the definitions it has for that word from any of the sources in the database. A word may provide definitions from Webster's 1913 dictionary, WordNet 2.0, and the Free Online Dictionary of Computing, among other sources. Webster's 1913 dictionary does contain pronunciation and quotations using the word. WordNet 2.0 provides synonyms. At the end of all the entries is a list of related words.
Because the basis of this dictionary is copyright free information, there are a number of modern words which are not included. The dictionary contains a link to add additional words to the dictionary, at the Online Community Dictionary. To add a word, you enter the word, the part of speech, the definition, and a sample sentence. All entries are reviewed by humans, and promotional material and external links are removed. Because of the number of modern words currently missing from the dictionary, care must be taken not to use wording taken from any copyrighted dictionary in creating definitions or in sample sentences.