straight face

 繃著臉

?含義：

an emotionless facial expression

沒(méi)有表情的臉

?例句：

I thought he was kidding when he told me his ridiculous plan, but he had a straight face the whole time.

當(dāng)他跟我說(shuō)起他那愚不可及的計(jì)劃時(shí)，我以為他在開(kāi)玩笑，但是他全程都是繃著臉的呀。

?對(duì)話：

A: So what exactly did you say to my father? He has kept that straight face. 

所以你到底跟我爸說(shuō)了啥，他現(xiàn)在一直繃著臉。

B: I just made a few jokes, but I guess I need to explain to him right now.

我就是開(kāi)了幾句玩笑，不過(guò)我覺(jué)得我現(xiàn)在得向他解釋一下了。

?額外收獲： 

ridiculous: adj.荒唐的、可笑的

make jokes：開(kāi)玩笑