designated driver
US /ˌdez.ɪɡ.neɪ.tɪd ˈdraɪ.vər/
UK /ˌdez.ɪɡ.neɪ.tɪd ˈdraɪ.vər/

1.
指定ドライバー, ハンドルキーパー
a person in a group who is chosen to drive everyone home safely after drinking alcohol, and who therefore does not drink any alcohol themselves
:
•
I'm the designated driver tonight, so no drinks for me.
今夜は私が指定ドライバーなので、お酒はなしです。
•
They took turns being the designated driver for their group outings.
彼らはグループでの外出で、交代で指定ドライバーを務めた。