The term 'brown study' is used to describe a state of deep thought or contemplation. The crossword solutions for this term include ABSORPTION (10 letters), REVERIE (7 letters), ABSTRACTION (11 letters), PREOCCUPATION (13 letters), THINK (5 letters), mused (5 letters), MUSE (4 letters), DAYDREAM (8 letters), and LEARNING (8 letters). All of these words refer to activities that involve deep thought or contemplation, such as being absorbed in thought, daydreaming, or LEARNING something new.