'Sardonic grin' definitions:

Definition of 'Sardonic grin'

From: GCIDE

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. [1913 Webster]
Where strained, sardonic smiles are glozing still, And grief is forced to laugh against her will. --Sir H. Wotton. [1913 Webster]
The scornful, ferocious, sardonic grin of a bloody ruffian. --Burke. [1913 Webster]
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. [1913 Webster]