It's a dictionary of synonyms and antonyms, and can be found:
* Online: Numerous websites like Thesaurus.com, Merriam-Webster, and Dictionary.com have integrated thesauruses.
* In word processing software: Many programs like Microsoft Word and Google Docs have built-in thesaurus functions.
* In physical dictionaries: Some dictionaries have a thesaurus section or are combined thesaurus/dictionary books.