不得而知bùdé'érzhīTop 25000Meanings1. unknown2. unable to find outCharacters used不no得to obtain而and知to knowExamples2这个zhège计划jìhuà能否néngfǒu成功chénggōng还hái不得而知bùdé'érzhī。It is yet to be seen whether this plan will succeed or not.当然dāngrán，那些nàxiē热水瓶rèshuǐpíng是不是shìbushì他们tāmen自己zìjǐ的de就jiù不得而知bùdé'érzhī了le。Obviously, we don't know if those thermos flasks are their own.