Source : Webster's Revised Unabridged Dictionary (1913)

Hydrofluoric \Hy`dro*flu*or"ic\, a. [Hydro-, 2 + fluoric.]
   (Chem.)
   Pertaining to, or containing, hydrogen and fluorine;
   fluohydric; as, hydrofluoric acid.

   {Hydrofluoric acid} (Chem.), a colorless, mobile, volatile
      liquid, {HF}, very corrosive in its action, and having a
      strong, pungent, suffocating odor. It is produced by the
      action of sulphuric acid on fluorite, and is usually
      collected as a solution in water. It attacks all
      silicates, as glass or porcelain, is the agent employed in
      etching glass, and is preserved only in vessels of
      platinum, lead, caoutchouc, or gutta-percha.

Source : WordNet®

hydrofluoric acid
     n : a weak poisonous liquid acid; formed by solution of hydrogen
         fluoride in water