chloroquinePronunciation: /ˈklɔːrə(ʊ)kwiːn, ˈklɒ-/Definition of chloroquine noun [mass noun] Medicine a synthetic drug related to quinoline, used against malaria. Origin: 1940s: from chloro- + quin(olin)echloroquine in other Oxford dictionaries Definition of chloroquine in the US English dictionary