A lack of facial expression; a blank or expressionless face that shows little emotion.
彼は無表情で質問に答えた。
He answered the question with an expressionless face.
面接のとき、緊張して無表情になってしまった。
I got so nervous during the interview that I became expressionless.
無表情のまま彼女は手紙を読み終えた。
She finished reading the letter without changing her expression.