chlorothiazide Syllabification: (chlo·ro·thi·a·zide)Pronunciation: /ˌklôrōˈTHīəˌzīd/Definition of chlorothiazide noun Medicine a synthetic drug used to treat fluid retention and high blood pressure. It is one of the thiazide diuretics. chlorothiazide in other Oxford dictionaries Definition of chlorothiazide in the British & World English dictionary