[the.sau.rus] n, pl -sau.ri or -sau.rus.es [NL, fr. L, treasure, collection, fr. Gk thesauros] (ca. 1823) 1: treasury, storehouse
2. a: a book of words or of information about a particular field or set of concepts; esp: a book of words and their synonyms b: a list of subject headings or descriptors usu. with a cross-reference system for use in the organization of a collection of documents for reference and retrieval -- the.sau.ral adj