be lost in space

To be completely confused about, unaware of, or out of touch with reality. Well, she's lost in space if she thinks she actually did a good job on this assignment. I had to fix tons of editorial mistakes! It's like he's lost in space or something. His instructions don't even make any sense. A: "Are you lost in space? How do you not know how to use a microwave?" B: "I've just never used one this fancy before!"