promethazinePronunciation: /prə(ʊ)ˈmɛθəziːn/Definition of promethazine noun [mass noun] Medicine a synthetic antihistamine drug derived from phenothiazine, used chiefly to treat the symptoms of allergies and motion sickness. Origin: 1950s: from pro(pyl) + (di)meth(ylamine), a colourless gas + (phenothi)azinepromethazine in other Oxford dictionaries Definition of promethazine in the US English dictionary
