The end of a statement that is not debateable, or emphasis on the firmness of your statement.
Jill's mom hates me so im not going to her house, Perius.
1-To dominate someone in a game everytime you play them, or to have absolute control over your opponents strategies.
'Man I freakin mastered Johns terran defense.'
'Dood Im not playing 3rd strike with karen anymore, I mastered her like 20 games in a row.'