If someone is impassive or their face is impassive, they are not showing any emotion.
例句
He searched Hill's impassive face for some indication that he understood...他盯着希尔毫无表情的面孔,寻找着表明他已明白的些许迹象。As the foreman of the jury announced the verdict, Miss Allan remained impassive.陪审团主席宣布裁决时,艾伦小姐一直面无表情。
英汉词典释义
adv.
无感情地;无表情地;无动于衷地
Pym listened impassively until the woman had finished.皮姆一直无动于衷地听着,直到那个女人说完。