Psychologically, emotionally, or intellectually separated from the outside world or from realistic, logical thought. When my mental illness was at its worst, I became completely detached from reality. The council's plan to build an interstate through the middle of town is just nonsense, it's completely detached from reality!

Psychologically, emotionally, intellectually, or physically separated from the people, influence, or average thinking of the outside world. He just keeps to himself, never talking to anyone, like he's detached from the world. He builds all of his policies from theory and what he studied in books—it's all completely detached from the outside world. The tiny rural village, totally detached from the outside world, developed a dialect and manner totally unique to the rest of the region.

To separate someone or something from its connection to someone or something else. This phrase can be used literally or figuratively. I detached the broken shutters from the house. When the teacher realized that I was the one talking, she detached me from the rest of my classmates for a scolding.