coprophagous grin

coprophagous grin

A smug, self-satisfied, or overly pleased smile, especially one that (intentionally or unintentionally) irritates others. A humorous literalization of the phrase "shit-eating grin" (where coprophagia, or coprophagy, means the ingestion of feces). She's been walking around with that coprophagous grin on her face ever since she found out she got into Harvard.
See also: grin