fish-eating grin (plural fish-eating grins)
- (idiomatic) A broad smile indicating self-awareness that may suggest self-satisfaction, smugness, discomfort, or embarrassment.
2002, Brian Cruver, Anatomy of greed: The Unshredded Truth from an Enron Insider, →ISBN, page 337:
I had a few questions for him myself, but I just stood there and stared. He had a fish-eating grin on his face.
2008, Joel Stratte-McClure, The Idiot and the Odyssey: Walking the Mediterranean, →ISBN:
Then the Gypsy makes a crack about my accent. "You talk like a Spanish cow," he says with a fish-eating grin.