'Masu' is a nickname recently being used for professional DJ's, usually with the name 'Thomas' . Masu's are generally very skilled at their work and know exactly how and when to drop the beat. In parties, he leaves everyone amazed, and they all just scream for more music. A Masu is a cool DJ.
Guy 1 : "Who was Djing yesterday at the party yesterday? He was amazing!"
Guy 2 : "That was Masu, isn't he a cool DJ?!"