deep in thought

Từ điển WordNet v3.1 - WordNet Dictionary

adjective

deeply absorbed in thought (Freq. 1)
- as distant and bemused as a professor listening to the prattling of his freshman class
- lost in thought
- a preoccupied frown
• Syn:
bemused, lost, preoccupied
• Similar to:
thoughtful
• Derivationally related forms:
preoccupancy (for: preoccupied)