The Collaborative International Dictionary of English v.0.48:

Hydriodic \Hy`dri*od"ic\, a. [Hydr- + iodic: cf. F.
   hydriodique.] (Chem.)
   Pertaining to, or derived from, hydrogen and iodine; -- said
   of an acid (HI) produced by the combination of these
   elements.
   [1913 Webster]

   Hydriodic acid (Chem.), a pungent, colorless gas, HI,
      usually prepared as a solution in water. It is strong
      reducing agent. Called also hydrogen iodide.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hydriodic acid
    n 1: (HI) a colorless or yellow aqueous solution of hydrogen
         iodide; "hydriodic acid is a strong acid"