master definition

1. directs the work of others
2. an original creation (i.e., an audio recording) from which copies can be made
3. an officer who is licensed to command a merchant ship
4. someone who holds a master's degree from academic institution
5. an authority qualified to teach apprentices
6. be or become completely proficient or skilled in
• examples: She mastered Japanese in less than two years
7. have a firm understanding or knowledge of; be on top of
• examples: Do you control these data?