The Collaborative International Dictionary of English v.0.48:

Dope \Dope\ (d[=o]p), n. [D. doop a dipping, fr. doopen to dip.
   Cf. Dip.]
   1. Any thick liquid or pasty preparation, as of opium for
      medicinal purposes, of grease for a lubricant, etc.
      [Webster 1913 Suppl.]

   2. Any preparation, as of opium, used to stupefy or, in the
      case of a race horse, to stimulate. [Slang or Cant]
      [Webster 1913 Suppl.]

   3. An absorbent material; esp., in high explosives, the
      sawdust, infusorial earth, mica, etc., mixed with
      nitroglycerin to make a damp powder (dynamite, etc.) less
      dangerous to transport, and ordinarily explosive only by
      suitable fulminating caps.
      [Webster 1913 Suppl.]

   4. Information concerning the previous performances of race
      horses, or other facts concerning them which may be of
      assistance in judging of their chances of winning future
      races; similar information concerning other sports; by
      extension, any information not generally known, especially
      when coming from an inside source; as, the inside dope.
      [Sporting Slang]
      [Webster 1913 Suppl. +PJC]

   5. an ignorant or stupid person. [Colloq.]
      [PJC]

   get the dope on learn the true story; get the inside
      information.