She stared at me with a blank expression on her face.

她木然地盯着我。

《牛津词典》

Your blank expression, and the faraway look in your eyes are the cues that betray you inattentiveness.

你面无表情、眼神恍惚，这些都是你心不在焉的表现。

youdao

In it, a mother is asked to interact with her child in a normal way before putting on a blank expression and not giving them any visual social feedback.

实验中，一位母亲被要求以正常的方式与她的孩子互动，然后面无表情，不给他们任何视觉上的社交反馈。

youdao

As Juliette, Kristin Scott Thomas is first seen in closeup without makeup, her hair lustreless, her expression blank but tense.

NEWYORKER: I've Loved You So Long

His body was limp, his expression blank.

CNN: ASIANOW - TIME Asia | The Agony of Defeat

"Tabula rasa, " in the Latin expression: blank slate.

CNN: In the new year, be a first responder