A smug grin is a facial expression that conveys a sense of self-satisfaction or superiority. It is often characterized by a slight SMIRK and a raised corner of the mouth. The term 'smug grin' is often used interchangeably with the word 'SMIRK, ' which is defined as a facial expression of contempt or derision. Smug grins are often seen in people who feel they have outsmarted someone else or achieved something that others have not.