Source : Webster's Revised Unabridged Dictionary (1913)

Hydriodic \Hy`dri*od"ic\, a. [Hydr- + iodic: cf. F.
   hydriodique.] (Chem.)
   Pertaining to, or derived from, hydrogen and iodine; -- said
   of an acid produced by the combination of these elements.

   {Hydriodic acid} (Chem.), a pungent, colorless gas, {HI},
      usually prepared as a solution in water. It is strong
      reducing agent. Called also {hydrogen iodide}.

Source : WordNet®

hydrogen iodide
     n : a colorless gas that yields hydroiodic acid in aqueous
         solution