open secret 公開的祕密
英文釋義
Something that everyone knows, but that is supposed to be a secret.
例句
Since they have been in love since being in high school together, it's an open secret that my sister is going to marry my best friend.
我妹妹打算和我最好的朋友結婚,這已經是公開的祕密,因爲他們在上高中時一直在談戀愛。