Source : Webster's Revised Unabridged Dictionary (1913)

Laudanum \Lau"da*num\, n. [Orig. the same wort as ladanum,
   ladbdanum: cf. F. laudanum, It. laudano, ladano. See
   {Ladanum}.]
   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}.

Source : WordNet®

laudanum
     n : narcotic consisting of a tincture of opium or any
         preparation in which opium is the main ingredient [syn: {tincture
         of opium}]