noun, plural the·sau·rus·es, the·sau·ri [-sawr-ahy] /-ˈsɔr aɪ/.
- a dictionary of synonyms and antonyms, such as the online Thesaurus.com.
- any dictionary, encyclopedia, or other comprehensive reference book.
- a storehouse, repository, or treasury.
- an index to information stored in a computer, consisting of a comprehensive list of subjects concerning which information may be retrieved by using the proper key terms.
- a dictionary of synonyms and antonyms stored in memory for use in word processing.
noun plural -ruses or -ri (-raɪ)
- a book containing systematized lists of synonyms and related words
- a dictionary of selected words or topics
- rare a treasury
n.1823, “treasury, storehouse,” from Latin thesaurus “treasury, treasure,” from Greek thesauros “a treasure, treasury, storehouse, chest,” from root of tithenai “to put, to place.” The meaning “encyclopedia filled with information” is from 1840, but existed earlier as thesaurarie (1590s), used as a title by early dictionary compilers. Meaning “collection of words arranged according to sense” is first attested 1852 in Roget’s title. Thesaur is attested in Middle English with the meaning “treasure” (15c.-16c.).