When a face is inexpressive, it does not show what the person feels. The eyes, mouth, and brows stay still, so you cannot read joy, anger, or surprise there. People also use it for a voice, a look, or even a piece of writing that gives nothing away. It is a quiet, slightly formal word: a friend might just say you can't tell what she is feeling, or that her face didn't move. Though actually, an inexpressive face is not always a cold heart — some people are shy, some are tired, some have learned to hide their feelings, and some faces simply do not “talk” much. It is the not-showing partner of expressive, which is a face or voice that shows a lot.