Short for "Master Tool", typically used to describe someone who sucks up to and does random shit for others. Also connotative of someone who is acting effeminate and showing a girl his "sensitive side" just to get some pooty.
Usually screamed repeatedly in a high-pitched voice (pronounced "Masta Teeeee!") by a group of people witnessing another person acting like a huge tool. The screams are oftentimes accompanied by the same gesture that referees use to call for a "time out".
See also: Gofer
Boy 1: I totally think you should break up with Derek. He has no respect for you and just wants to get in your pants.
Girl 1: (Crying, hugs Boy 1) Thank God I have you, otherwise I have no idea what I would do with myself!
Onlooker 1: What a fuckin' Master T.
Onlooker 2: Seriously. I wonder if he has a mangina. (Screaming) MASTAA TEEEEE