Source : Webster's Revised Unabridged Dictionary (1913)

Sardonic \Sar*don"ic\, a.
   Of, pertaining to, or resembling, a kind of linen made at
   Colchis.

Sardonic \Sar*don"ic\, a. [F. sardonique, L. sardonius, Gr. ?,
   ?, perhaps fr. ? to grin like a dog, or from a certain plant
   of Sardinia, Gr. ?, which was said to screw up the face of
   the eater.]
   Forced; unnatural; insincere; hence, derisive, mocking,
   malignant, or bitterly sarcastic; -- applied only to a laugh,
   smile, or some facial semblance of gayety.

         Where strained, sardonic smiles are glozing still, And
         grief is forced to laugh against her will. --Sir H.
                                                  Wotton.

         The scornful, ferocious, sardonic grin of a bloody
         ruffian.                                 --Burke.

   {Sardonic grin} or {laugh}, an old medical term for a
      spasmodic affection of the muscles of the face, giving it
      an appearance of laughter.

Source : WordNet®

sardonic
     adj : disdainfully or ironically humorous; scornful and mocking;
           "his rebellion is the bitter, sardonic laughter of all
           great satirists"- Frank Schoenberner; "a wry pleasure
           to be...reminded of all that one is missing"- Irwin
           Edman [syn: {wry}]