grin/smile from ear to ear to look extremely happy 非常开心，笑得合不拢嘴 smile from ear to ear 的字面意思是“笑容从左耳到右耳”，那可不就是“笑得合不拢嘴”嘛！ "We've had a fantastic response!" he said, grinning from ear to ear. “我们收到的反馈极好，”他说着，笑得嘴都合不拢了。