/ θɪˈsɔːrəs; NAmE / noun
( pl. the·sauri / θɪˈsɔːraɪ; NAmE / or the·saur·uses / -rəsɪz; NAmE /) a book that is like a dictionary, but in which the words are arranged in groups that have similar meanings
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WORD ORIGIN
late 16th cent.: via Latin from Greek thēsauros storehouse, treasure. The original sense dictionary or encyclopedia was narrowed to the current meaning by the publication of Roget's Thesaurus of English Words and Phrases (1852).