>Melancholy mood accompanied by deep thought
>Preoccupied
>A moody daydream
>Not paying attention or concentrating on the matter in hand
>Intense, or deep absorption in own thoughts
>A state of abstraction, absent-mindedness, or deep thought
>Black mood
>Gloomy meditations
Example
>Chloe was so engrossed in a brown study that she didn’t hear the doorbell.
>He was so deep in a brown study on his way home that he missed his turning.