papaverinePronunciation: /pəˈpeɪvərʌɪn, -ˈpav-, -iːn/Definition of papaverine noun [mass noun] Chemistry a compound present in opium used medicinally to alleviate muscle spasm and asthma. An alkaloid; chemical formula: C20H21NO4 Origin: mid 19th century: from Latin papaver 'poppy' + -ine4papaverine in other Oxford dictionaries Definition of papaverine in the US English dictionary