as sober as a judge 十分清醒，非常严肃

【例句】
I had expected him to be angry, but instead he sat quietly at his desk, as sober as a judge.
我以为他会发火，但他却不声不响地坐在办公桌旁，像法官一样镇静自若。

They're an odd pair of friends, Sylvia always bubbling over with nonsense and Polly as sober as a judge.
她们是一对奇特的朋友，西尔维亚老是抑制不住胡言乱语，而波利却十分庄重严肃。