Domineering describes a person who is arrogant and bossy, like a military dictator or a supervisor who micromanages everyone at work.
People who are strong-willed and overbearing can be described as domineering, like customers in a restaurant who demand things with snappy fingers. Parents who say sternly to their kids, "Because I say so, that's why," are speaking in a domineering way. The word domineering comes from the Latin root dominari, "to rule or 'lord' it over."