1) Gloomy expression 2) Glum expression 3) Look of melancholy 4) Look of sadness 5) Obvious sign of sadness 6) Sad look 7) Sign of sadness 8) Sullen expression 9) Unhappy expression 10) What pouting people put on 
an unhappy or gloomy expression: He's been walking around with a long face ever since he failed the examination.