If a face or a voice is expressionless, it gives you nothing you can read — no smile, no frown, no warmth, no clear anger. The person may be hiding a feeling on purpose (a poker face), or they may be in shock, tired, or very still. It is a common adjective in stories; in very casual talk people more often say he showed nothing or her face didn’t move. Though actually, it describes the look or the sound, not the person as a whole. An expressionless face can still belong to someone who feels a great deal. A voice can be expressionless too: the words come out flat, with no music of feeling.

面無表情的