tiān​zhī​dì​zhī​nǐ​zhī​wǒ​zhī

a secret known only to us

Senses

天知地知你知我知 tiān​zhī​dì​zhī​nǐ​zhī​wǒ​zhī a secret known only to us

lit. heaven knows, earth knows, you know and I know; used to describe a secret that is supposedly confidential but is actually known by multiple parties or will inevitably be revealed

References

see 四知/四知 天知地知你知我知/天知地知你知我知