chlorothiazidePronunciation: /ˌklɔːrə(ʊ)ˈθʌɪəzʌɪd, ˈklɒ-/Definition of chlorothiazide noun [mass noun] Medicine a synthetic drug used to treat fluid retention and high blood pressure. chlorothiazide in other Oxford dictionaries Definition of chlorothiazide in the US English dictionary