This is a slang term for the city of Minot (a.k.a "Mindrot") North Dakota. Which is a very appropriate name considering the people who are born and raised in the town (and never leave) pretty much sit at home and watch tv 24/7 and literally allow their minds to rot. Funny what too much religion and limited exposure to the outside world can do to a person.
"Hi Steve, how are you? I haven't talked to you for along time! What? You're STILL living in Mindrot, North Dakota?! I'm sorry. What's the temp? -8 degrees? Geesh! Well I better let you go so you can go watch TV or go back to church."