Master

Concise Oxford English Dictionary © 2008 Oxford University Press:
master1

▶noun

• 1 chiefly historical a man who has people working for him, especially servants or slaves.

  ■ dated a male head of a household.

  ■ the male owner of a dog, cat, etc.

• 2 a skilled practitioner of a particular art or activity.

  ■ a great artist, especially one belonging to the accepted canon.

  ■ a very strong chess player.

  ■ (Masters) [treated as sing.] (in some sports) a class for competitors over the usual age for the highest level of competition.

• 3 a person who has complete control of something: he was master of the situation.

• 4 a man in charge of an organization or group.

  ■ Brit. a male schoolteacher, especially at a public or prep school.

  ■ the head of a college or school.

  ■ the presiding officer of a livery company or Masonic lodge.

  ■ the captain of a merchant ship.

  ■ (in England and Wales) an official of the Supreme Court.

• 5 [usu. in titles] a person who holds a second or further degree: a master's degree.

• 6 a title prefixed to the name of a boy.

• 7 a machine or device directly controlling another. Compare with slave.

• 8 an original film, recording, or document from which copies can be made.

▶adjective

• 1 having or showing very great skill or proficiency.

  ■ denoting a person skilled in a particular trade and able to teach others: a master builder.

• 2 main; principal: the master bedroom.

▶verb

• 1 acquire complete knowledge or skill in.

• 2 gain control of; overcome.

• 3 make a master copy of (a film or record).

– derivatives
masterless adjective,
mastership noun.

– origin OE mæg(i)ster, from L. magister.

Concise Oxford English Dictionary © 2008 Oxford University Press:
master2

▶noun a ship or boat with a specified number of masts: a three-master.