<p><strong>Noun</strong></p><ul><li>Pharmacology: a poisonous crystalline alkaloid, C₁₇H₂₃NO₃, obtained from belladonna and other plants of the nightshade family, that prevents the response of various body structures to certain types of nerve stimulation.</li><li>Used chiefly to relieve spasms, to lessen secretions, and, topically, to dilate the pupil of the eye.</li></ul>