 
A list of subject headings or descriptors usually with a cross-reference system for use in the organization of a collection of documents for reference and retrieval.
http://beautifulsynonyms.com/ 
 Also offers antonyms and definitions.
http://graphwords.com/ 
 Produces a color coded graph using data taken from the Wordnet lexicon for the chosen word, showing associations. Graphs can be saved and printed.
http://www.lexfn.com/ 
 Search for relationships between words and concepts that might never have occurred to you before.
http://www.merriam-webster.com/thesaurus 
 Provides synonyms, antonyms, related words and idiomatic phrases.
http://www.phrases.org.uk/phrase-thesaurus/ 
 A resource for writers. Enter a single word and it will return a list of phrases and sayings that are related to the word in some way. In English.
https://www.powerthesaurus.org/ 
 Also offers broader, narrower and related synonyms.
http://www.synonyms.net/ 
 Includes word-related facts and word of the day.
http://www.synonyms360.com/ 
 Provides a searchable database and a partial word index to browse.
http://www.thesaurus.com/ 
 Online version of Roget's II: The New Thesaurus, 3rd edition.
http://www.visualthesaurus.com/ 
 Interactive dictionary and thesaurus using a visual display for data navigation.
http://www.wordsmyth.net/ 
 Integrated English dictionary and thesaurus.
Thanks to DMOZ, which built a great web directory for nearly two decades and freely shared it with the web. About us