lost in thought
Definitions
Deeply absorbed in one's own reflections or daydreams.
Inattentive to one's immediate surroundings due to intense mental focus.
Examples
She was so lost in thought that she didn't hear me walk into the room.
He sat on the park bench for hours, completely lost in thought as the sun began to set.
Synonyms
deep in contemplation preoccupied pensive absent-minded lost in reverie engrossed introspective