absorbed in thought
Fully and deeply engrossed in a thought or idea, often to such a degree as to be unaware of or insensitive to the outside world. It's no use trying to talk to Helen when she's absorbed in thought like that; it's as if we don't even exist! Sorry, what did you say? I was absorbed in thought there. A: "Hey, did you hear the phone ring?" B: "Oh wow, no, I didn't. I guess I've been absorbed in thought."
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.