open secret 公开的秘密
英文释义
Something that everyone knows, but that is supposed to be a secret.
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结婚，这已经是公开的秘密，因为他们在上高中时一直在谈恋爱。