Thesauri

noun

1. A publication, usually in the form of a book, that provides synonyms (and sometimes antonyms) for the words of a given language.

   ""Roget" is the leading brand name for a print English thesaurus that lists words under general concepts rather than just close synonyms."

2. A dictionary or encyclopedia.
3. A hierarchy of subject headings — canonic titles of themes and topics, the titles serving as search keys.