What does "laudanum" mean?

Laudanum: Tincture of opium, used for various medical purposes. Note: A fluid ounce of American laudanum should contain the soluble matter of one tenth of an ounce avoirdupois of powdered opium with equal parts of alcohol and water. English laudanum should have ten grains less of opium in the fluid ounce. U. S. Disp. Dutchman's laudanum (Bot.) See under Dutchman.