muscarinePronunciation: /ˈmʌskəriːn, -ɪn/Definition of muscarine noun [mass noun] Chemistry a poisonous compound present in certain fungi, including the fly agaric. An alkaloid; chemical formula: C9H21NO3 Origin: late 19th century: based on Latin musca 'fly'muscarine in other Oxford dictionaries Definition of muscarine in the US English dictionary