what is a thesaurus
thesaurusnoun [ C ] uk â /Î¸ÉªËsÉË.rÉs/ us â /Î¸ÉªËsÉËr.És/ plural thesauruses or formal thesauri uk â /Î¸ÉªËsÉË.raÉª/ us â /-ËsÉËr.aÉª/. âº a type of dictionary in which words with similar meanings are arranged in groups. Thesaurus: synonyms and related words. Books: reference books. almanac. annual.