Someone (usually a woman, but it can also be a man), who thinks they are right about something when they are actually wrong. They are usually very demanding, and very disrespectful, and rude to a cashier, and/or worker. They more often than not "Demand to see your manager," in an attempt to get you fired and/or file a complaint. But it's also when you come in contact with one, they are usually bossy, tell you what to do/not to do. They get in your business. Etc.
