Dumbgeon Master

A host of a Tabletop role-playing game such as DnD that is ill-prepared, organizing the game poorly and/or simply being dumb.
Jokingly said to generally good dms having a bad day, or as an actual insult to an idiot Dm ruining the game.

Player: Im going to attack this guy!
Dm: Uhhh okay, roll for persuasion
Player: what?? That doesnt make sense, you dumbgeon master