This is Artha online, which is an English Thesaurus based on WordNet. Wordnet is a big lexical database of the English language that was implemented at the Princeton University.
Available at: http://www.offidocs.com/index.php/desktop-online-utilities-apps/artha-free-thesaurus-dictionary
Artha online main features
- It is based on WordNet.
- Regular expressions based search using wildcards.
- History of all the search terms carried out.
- Previous and Next buttons to easily navigate through all the searches
- Spelling suggestions
- For each word searched Arthas include the following:
Synonyms,
Similar Terms,
Domain Terms,
Antonyms,
Derivatives,
Pertainyms (related noun/verb),
Attributes,
Entails (what a verb entails doing),
Causes (what a verb causes to),
Hypernyms (is a kind of),
Hyponyms (kinds),
Holonyms (is a part of)
Meronyms (parts)
Further instructions can be found at http://artha.sourceforge.net.