Claim: A frown is used to express anger and displeasure.
Evidence: A frown (also known as a scowl) is a facial expression in which the eyebrows are brought together, and the forehead is wrinkled, usually indicating displeasure, sadness or worry, or less often confusion or concentration. In fact, frowning as a component of anger or disgust is widely recognized as a universal expression easily recognized across cultures. 
In social settings frowns are most frequently used to express a range of negative emotions including anger and displeasure.