n., pl. thesauruses or thesauri a list of words with related meanings, including synonyms and antonyms a specialized vocabulary of words and phrases, commonly used for indexing, that indicates a preferred term among synonyms and shows relationships between terms


A thesaurus is distinguished from dictionaries and glossaries, the latter not establishing a preferred term among synonymous terms. A thesaurus often contains nothing more than headings and their relationships, where dictionaries and glossaries usually contain definitions and annotations on word use.