mas·ter 
(măstər)
(măstər)n.
1. One that has control over another person, a group of persons, or a thing, especially:
a. The owner or keeper of an animal: The dog ran toward its master.
b. The owner of a slave.
c. One who has control over or ownership of something: the master of a large tea plantation.
d. An employer.
e. The man who serves as the head of a household.
f. One who defeats another; a victor: I had to admit that I had met my master and so conceded the game.
g. One who acts out the role of the dominating partner in a sadomasochistic relationship.
2. The captain of a merchant ship. Also called master mariner.
3.
a. One whose teachings or doctrines are accepted by followers.
b. Master Christianity Jesus.
4. A male teacher, schoolmaster, or tutor.
5. One who holds a master's degree.
6.
a. An artist or performer of great and exemplary skill.
b. An old master.
7. A worker qualified to teach apprentices and carry on the craft independently.
8. An expert: a master of three languages.
9. Abbr. M.
a. Used formerly as a title for a man holding a naval office ranking next below a lieutenant on a warship.
b. Used as a title for a man who serves as the head or presiding officer of certain societies, clubs, orders, or institutions.
c. Master Used as a title for any of various male officers having specified duties concerning the management of the British royal household.
d. Master Used as a courtesy title before the given or full name of a boy not considered old enough to be addressed as Mister.
e. Archaic Used as a form of address for a man; mister.
10. One who is appointed to assist a court in the performance of certain legal functions, such as the taking of testimony and calculating damages in complex litigation. Also called special master.
11. Master A man who owns a pack of hounds or is the chief officer of a hunt.
12. An original, such as an original document or audio recording, from which copies can be made.
adj.
1. Of, relating to, or characteristic of a master.
2. Principal or predominant: a master plot.
3. Controlling all other parts of a mechanism: a master switch.
4. Highly skilled or proficient: a master thief.
5. Being an original from which copies are made.
tr.v. mas·tered, mas·ter·ing, mas·ters
1. To become very skilled in or knowledgeable about: mastered the language in a year's study.
2. To overcome or defeat: He finally mastered his addiction to drugs.
3. To produce a master copy of (an audio or video recording, for example).
[Middle English maister, master, from Old English māgister, mægister and Old French maistre, both from Latin magister; see meg- in the Appendix of Indo-European roots.]
master·dom n.