Definition of "Master" :

noun: an original creation (i.e., an audio recording) from which copies can be made

noun: key that secures entrance everywhere

noun: presiding officer of a school

noun: an artist of consummate skill

"A master of the violin."

noun: an authority qualified to teach apprentices

noun: directs the work of others

noun: someone who holds a master's degree from academic institution

noun: an officer who is licensed to command a merchant ship

noun: a person who has general authority over others

noun: a combatant who is able to defeat rivals

verb: have a firm understanding or knowledge of; be on top of

verb: be or become completely proficient or skilled in

"She mastered Japanese in less than two years."

verb: get on top of; deal with successfully

verb: have dominance or the power to defeat over

"Her pain completely mastered her."

adjective: most important element

"The master bedroom."