1) Absorbed 2) Bemused 3) Deep in thought 4) Deeply absorbed in thought 5) Filled 6) Lost 7) Previously occupied 8) Taken 9) Thoughtful Found on https://www.crosswordclues.com/clue/preoccupied
[Adjective] If you are preoccupied you are busy thinking about something else. Example: I tried to concentrate at work but I was preoccupied with my mothers illness.
Found on http://www.bbc.co.uk/skillswise/glossary/
completely engrossed in thought; absorbed. · previously occupied; taken; filled. · already used as a name for some species, genus, etc., and not available as a designation for any other. Found on https://www.infoplease.com/dictionary/preoccupied