Pronunciation: (bel"u-don'u),[key] —n. 1. Also called deadly nightshade. a poisonous plant, Atropa belladonna, of the nightshade family, having purplish-red flowers and black berries.
2. Pharm.a drug from the leaves and root of this plant, containing atropine and related alkaloids: used in medicine to check secretions and spasms, to relieve pain or dizziness, and as a cardiac and respiratory stimulant.