the•sau•rus (θɪˈsɔr əs)
n., pl. -sau•rus•es, -sau•ri (-ˈsɔr aɪ)
1. a dictionary of synonyms and antonyms.
2. any dictionary, encyclopedia, or other comprehensive reference book.
3. a storehouse, repository, or treasury.
[1730–40; < Latin thēsaurus < Greek thēsaurós treasure, treasury]
https://www.thefreedictionary.com/thesauruses