Used to describe a story or a joke that is only funny in context. Usually used to describe "You-Had-To-Have-Been-There" stories. Named after Meatwad from Aqua Teen Hunger Force for his ability to make seemingly unfunny things funny with his voice and tone of voice.
So we came up to the trash and she got her shirt stuck on the side! *Starts laughing*
Guy #2: (Not laughing)