\Bel`la*don"na\, n. [It., literally fine lady; bella
beautiful + donna lady.] (Bot.)
(a) An herbaceous European plant ({Atropa belladonna}) with
    reddish bell-shaped flowers and shining black berries.
    The whole plant and its fruit are very poisonous, and the
    root and leaves are used as powerful medicinal agents.
    Its properties are largely due to the alkaloid atropine
    which it contains. Called also {deadly nightshade}.
(b) A species of {Amaryllis} ({A. belladonna}); the
    belladonna lily.