Source : Webster's Revised Unabridged Dictionary (1913)

Master \Mas"ter\, v. t. [imp. & p. p. {Mastered}; p. pr. vb. n.
   {Mastering}.]
   1. To become the master of; to subject to one's will,
      control, or authority; to conquer; to overpower; to
      subdue.

            Obstinacy and willful neglects must be mastered,
            even though it cost blows.            --Locke.

   2. To gain the command of, so as to understand or apply; to
      become an adept in; as, to master a science.

   3. To own; to posses. [Obs.]

            The wealth That the world masters.    --Shak.

Source : WordNet®

mastering
     n 1: becoming proficient in the use of something; having mastery
          of; "his mastering the art of cooking took a long time"
     2: the act of making a master recording from which copies can
        be made; "he received a bill for mastering the concert and
        making 100 copies"