preoccupied
1. [ adjective ] deeply absorbed in thought
Synonyms: deep_in_thought lost bemused
Examples:

"as distant and bemused as a professor listening to the prattling of his freshman class" "lost in thought" "a preoccupied frown"

Related terms: thoughtful
2. [ adjective ] having or showing excessive or compulsive concern with something
Synonyms: obsessed taken_up haunted
Examples:

"became more and more haunted by the stupid riddle" "was absolutely obsessed with the girl" "got no help from his wife who was preoccupied with the children"

Related terms: concerned
Similar spelling:   preoccupy
  preoccupancy
  preoccupation
  Prociphilus
  Procopio