expression
living in obscurity; lying low; remaining unnoticed
Describes a person or thing that is not active or prominent, often with a nuance of being stuck in a quiet, unremarkable state. Commonly used for someone who has not yet achieved success or is biding their time.
彼は長年鳴かず飛ばずの生活を送っている。
He has been living in obscurity for many years.
あの俳優はまだ鳴かず飛ばずだが、いつかブレイクするかもしれない。
That actor is still lying low, but he might break through someday.