16th century, from Latin thēsaurus, from Ancient Greek θησαυρός (thēsauros, “storehouse, treasure”); its current English usage/meaning was established soon after the publication of Peter Roget's Thesaurus of English Words and Phrases in 1852
- 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.
- (archaic) A dictionary or encyclopedia.
- (information science) A hierarchy of subject headings—canonic titles of themes and topics, the titles serving as search keys.
Derived terms 
See also 
- thesaurus in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
- thesaurus in The Century Dictionary, The Century Co., New York, 1911
- Roget's Thesaurus can be found at: http://www.bartleby.com/thesauri
Alternative forms 
From Ancient Greek θησαυρός (thēsauros, “storehouse, treasure”).
- treasure, hoard
- a dear friend, loved one
- a vault for treasure
- chest, strongbox
- repository, collection