Source : Webster's Revised Unabridged Dictionary (1913)

Bay rum \Bay" rum"\
   A fragrant liquid, used for cosmetic and medicinal purposes.

   Note: The original bay rum, from the West Indies, is
         prepared, it is believed, by distillation from the
         leaves of the bayberry ({Myrcia acris}). The bay rum of
         the Pharmacop[oe]ia (spirit of myrcia) is prepared from
         oil of myrcia (bayberry), oil of orange peel, oil of
         pimento, alcohol, and water.

Source : WordNet®

bay rum
     n : an aromatic liquid originally obtained by distilling the
         leaves of the bayberry tree with rum