keep a straight face

• vi. 板着面孔(不露笑容)

例句

用作不及物动词 (vi.)

1. It seems to gaze with a steady face upon the city below.
   它似乎板着面孔凝视着下面的城市。
2. He maintains a poker face and you can't even guess what he's thinking.
   他板着面孔，你甚至无法猜测他在想些什么。