A Master

1. Someone who has control over something or someone.
2. The owner of an animal or slave.
3. (nautical) The captain of a merchant ship; a master mariner. Synonyms: skipper, captain
4. (dated) The head of a household.
5. Someone who employs others.
6. An expert at something.

Synonyms: skilled person

7. A tradesman who is qualified to teach apprentices.
8. (dated) A schoolmaster.
9. A skilled artist.
10. (dated) A man or a boy; mister.
11. A master's degree; a type of postgraduate degree, usually undertaken after a bachelor degree.

Synonyms: masters, master's, magistrate (Quebec English)

12. A person holding such a degree.
13. The original of a document or of a recording.
14. (film) The primary wide shot of a scene, into which the closeups will be edited later.Synonyms: establishing shot, long shot
15. (law) A parajudicial officer (such as a referee, an auditor, an examiner, or an assessor) specially appointed to help a court with its proceedings.
16. (engineering, computing) A device that is controlling other devices or is an authoritative source.

Synonym: primaryAntonyms: secondary, slave

17. (freemasonry) A person holding an office of authority, especially the presiding officer.
18. (by extension) A person holding a similar office in other civic societies.