master

noun

1.
an artist of consummate skill
3.
a combatant who is able to defeat rivals
4.
directs the work of others
Derived from:
mastership
5.
presiding officer of a school
Derived from:
mastership
6.
an original creation (i.e., an audio recording) from which copies can be made
8.
someone who holds a master's degree from academic institution
9.
an authority qualified to teach apprentices
10.
key that secures entrance everywhere