Source : Webster's Revised Unabridged Dictionary (1913)

Narcotic \Nar*cot"ic\, a. [F. narcotique, Gr. ??????????, fr.
   ??????? to benumb, na`rkh numbness, torpor.] (Med.)
   Having the properties of a narcotic; operating as a narcotic.
   -- {Nar*cot"ic*ness}, n.

Narcotic \Nar*cot"ic\, n. (Med.)
   A drug which, in medicinal doses, generally allays morbid
   susceptibility, relieves pain, and produces sleep; but which,
   in poisonous doses, produces stupor, coma, or convulsions,
   and, when given in sufficient quantity, causes death. The
   best examples are opium (with morphine), belladonna (with
   atropine), and conium.

         Nercotykes and opye (opium) of Thebes.   --Chaucer.

Source : WordNet®

narcotic
     adj 1: of or relating to or designating narcotics; "narcotic
            addicts"; "narcotic stupor"
     2: inducing stupor or narcosis; "narcotic drugs" [syn: {narcotizing},
         {narcotising}]
     3: inducing mental lethargy; "a narcotic speech" [syn: {soporiferous},
         {soporific}]

narcotic
     n : a drug that produces numbness or stupor; often taken for
         pleasure or to reduce pain; extensive use can lead to
         addiction