Noun

1. United states poet (1869-1950)
2. An artist of consummate skill
3. A person who has general authority over others
4. A combatant who is able to defeat rivals
5. Directs the work of others
6. Presiding officer of a school
7. An original creation (i.e., an audio recording) from which copies can be made
8. An officer who is licensed to command a merchant ship
9. Someone who holds a master's degree from academic institution
10. An authority qualified to teach apprentices
11. Key that secures entrance everywhere

Verb

1. Be or become completely proficient or skilled in
2. Get on top of; deal with successfully
3. Have dominance or the power to defeat over
4. Have a firm understanding or knowledge of; be on top of