Definitions of master:

• noun:   an original creation (i.e., an audio recording) from which copies can be made
• noun:   an authority qualified to teach apprentices
• noun:   directs the work of other
• noun:   someone who holds a master's degree from academic institution
• noun:   an officer who is licensed to command a merchant ship
• noun:   an artist of consummate skill

  Example: "A master of the violin"

• noun:   a person who has general authority over others
• noun:   a combatant who is able to defeat rivals
• noun:   presiding officer of a school
• noun:   key that secures entrance everywhere
• verb:   have a firm understanding or knowledge of; be on top of
• verb:   be or become completely proficient or skilled in

  Example: "She mastered Japanese in less than two years"

• verb:   have dominance or the power to defeat over

  Example: "Her pain completely mastered her"

• verb:   get on top of; deal with successfully
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #13713)