1. A person exercising absolute authority of any kind or in any sphere; one who authoritatively prescribes a course of action or says what is to be done: When a country is run by a dictator, he or she has total and complete command over the people and can often be very cruel.
2. A person who tells a writer what to put into print: When Johann Sebastian Bach was very old and became blind, he acted as a dictator when he told his son-in-law to write down the notes for his music.