The term Massiv Fagget refers to someone who disappoints his/her friends. Almost always used as a joke to show your disappointment.
Note: Always hold the M when saying this phrase.
eg. MMmmmmmmmassiv fagget!
Friend 2: Nah sorry, I'm kinda tired.
Friend 1: Ohhh, mmmmassiv fagget!
Friend 2: I know, I know, I'm sorry. We'll do something tomorrow.