RBF stands for "resting bitch face," which is a facial expression that unintentionally creates the impression that a person is angry, annoyed, irritated, or contemptuous, particularly when the individual is relaxed, resting, or not expressing any particular emotion. The term has gained popularity in recent years, with many people using it to describe their own or others facial expressions. While some people may use the term as a joke, research has shown that RBF is a real phenomenon and that people may judge a neutral, expressionless face to be "unfriendly". Cultural differences and gender bias may also play a role in peoples perception of RBF. Some scientists are interested in studying RBF to understand why some people have it and what it means in terms of a persons psychology.