shit-eating grin
nounEtymology
Possibly from a contraction of "grinning like a ’possum eating shit" (compare also happy as a pig in shit); later detached from meaning and persisting due to its vividness (cf. "there are many ways to skin a cat" or "happy as a clam").
Definitions
A broad smile indicating self-awareness that may suggest self-satisfaction, smugness,…
A broad smile indicating self-awareness that may suggest self-satisfaction, smugness, discomfort, or embarrassment.
- Near-synonym: smirk
- He was at the wheel of his brand-new 1965 GTO, top down, wearing a super-sized shit-eating grin on his face. 
The neighborhood
Vish — recursive loop
No curated loop yet for shit-eating grin. Loops are being traced one word at a time while the ingestion pipeline matures.
sense glosses and etymology drawn from English Wiktionary · source · CC-BY-SA