Source : Webster's Revised Unabridged Dictionary (1913)

Ferricyanic \Fer`ri*cy*an"ic\, a. [Ferri- + cyanic.] (Chem.)
   Pertaining to, or derived from, a ferricyanide.

   {Ferricyanic acid} (Chem.), a brown crystalline substance,
      {H6(CN)12Fe2}, obtained from potassium ferricyanide, and
      regarded as the type of the ferricyanides; -- called also
      {hydro-ferricyanic acid}, {hydrogen ferricyanide}, etc.

Source : WordNet®

ferricyanic acid
     n : a brown unstable acid formed from ferricyanide