Nouns

(n)maestro, masteran artist of consummate skill“a master of the violin”, “one of the old masters”
(n)overlord, master, lorda person who has general authority over others
(n)victor, master, superiora combatant who is able to defeat rivals
(n)masterdirects the work of others
(n)headmaster, schoolmaster, masterpresiding officer of a school
(n)master, master copy, originalan original creation (i.e., an audio recording) from which copies can be made
(n)master, captain, sea captain, skipperan officer who is licensed to command a merchant ship
(n)mastersomeone who holds a master's degree from academic institution
(n)master, professionalan authority qualified to teach apprentices
(n)passkey, passe-partout, master key, masterkey that secures entrance everywhere

Verbs

(v)master, get the hang, get the hang ofbe or become completely proficient or skilled in“She mastered Japanese in less than two years”
(v)overcome, get over, subdue, surmount, masterget on top of; deal with successfully“He overcame his shyness”
(v)dominate, masterhave dominance or the power to defeat over“Her pain completely mastered her”, “The methods can master the problems”
(v)master, controlhave a firm understanding or knowledge of; be on top of“Do you control these data?”

Adjectives

(s)chief, main, primary, principal, mastermost important element“the chief aim of living”, “the main doors were of solid glass”, “the principal rivers of America”, “the principal example”, “policemen were primary targets”, “the master bedroom”, “a master switch”