unattainable prize; something out of reach; flower on a high peak
Idiomatic expression for something highly desirable but impossible to obtain, often used for a romantic interest perceived as too good for oneself. Literally 'flower on a high peak'.
She is out of my league.
あの大学は高嶺の花で、合格は難しい。
That university is an unattainable prize; it's hard to get in.