生疏 (shēng shū): незнакомый

I haven't played the piano for ten years, and now my fingers are very rusty; I can't even play the simplest piece well.

He just transferred to a new department and is still unfamiliar with the workflow here, so he often needs colleagues' help.

Although we were neighbors as children, we lost touch for many years after moving, and now our relationship has become distant.

This veteran actor hadn't been on stage for a long time and was a bit rusty with his lines, but as soon as he heard applause, he got the feel back.

I lived abroad for five years, and when I first returned to Beijing, I was somewhat unfamiliar with the subway lines and almost took the wrong direction.