straight-faced

1. ADJ A straight-faced person appears not to be amused in a funny situation. 表情嚴肅的; 繃著臉的

...a straight-faced, humourless character. ...一個表情嚴肅、毫無幽默感的人。

"Whatever gives you that idea?" she replied straight-faced. “你怎麽會有那種想法呢?”她繃著臉答道。