A state of utter confusion that can be brought about in various ways, e.g. immediately after waking up, or hearing an unfamiliar inside joke. Some people are more prone to being murred out than others.
Matthew: I tried to go to class today, but I forgot that today is Labor Day. I spent 20 minutes sitting in the lecture hall waiting for the professor to show up.
Jack: Sounds like you were murred out, dawg.