grin

他无法掩饰脸上洋溢的欣喜笑容。

He couldn't hide the delighted ___grin that spread across his face.

他们之间交换了一个会意的笑容，心照不宣。

A knowing ___grin passed between them, acknowledging the shared secret.

当他揭晓惊喜时，一抹恶作剧般的咧嘴笑在他脸上漾开。

A mischievous ___grin spread across his face as he revealed the surprise.