What does atropine mean? atropine. Noun 1. (toxicology, pharmacology) ; An alkaloid extracted from the plant deadly nightshade (Atropa belladonna) ; and other sources. Though overdoses would be fatal it is used as a drug in medicine for its paralytic effects (e.g. in surgery to relax muscles, in dentistry to dry the mouth, in ophthalmology to dilate the pupils) ;.