To grin means to smile widely, showing your teeth. When you grin, you beam with happiness, amusement, or satisfaction, creating a big, unmistakable expression of joy. Picture a kid on Christmas morning tearing open presents, or a soccer player who just scored the winning goal. That big, unmistakable smile is a grin.

People grin when they're delighted, when they've pulled off something clever, or when they find something genuinely funny. You might grin at a friend's joke, grin with pride after acing a presentation, or grin mischievously when you're up to something playful.

The phrase grin and bear it means to endure something unpleasant without complaining, like grinning through a boring ceremony or a long car ride. Sometimes people describe someone as having a grin from ear to ear, which means their smile is so wide it seems to stretch across their entire face.