poker-faced

1. ADJ If you are poker-faced, you have a calm expression on your face that shows none of your thoughts or feelings. 面無表情的[非正式]

His expressions varied from poker-faced to blank. 他的表情在不露聲色與茫然之間變幻不定。

The officer listened, poker-faced. 那個官員面無表情地聽著。