DICT.TW Dictionary Taiwan
Sar·don·ic a. 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 Sardonic laugh, an old medical term for a spasmodic affection of the muscles of the face, giving it an appearance of laughter.