An example of preoccupied is a person who is texting while driving.
I was preoccupied with a deadline at work, and I forgot his birthday.
Maybe that was what he had been so preoccupied with lately.
I know you've been preoccupied, but everyone else has noticed his interest in you.
Alex continued to be preoccupied with his problem - whatever it was.
Kutuzov seemed preoccupied and did not listen to what the general was saying.
Pierre had the air of a man preoccupied with considerations which had no connection with the matter in hand.