Adjective

abstracted, preoccupied, absent, absentminded, distracted mean inattentive to what claims or demands consideration. abstracted implies absorption of the mind in something other than one's surroundings, and often suggests reflection on weighty matters.
// walking about with an abstracted air preoccupied often implies having one's attention so taken up by thoughts as to neglect others.
// too preoccupied with her debts to enjoy the meal absent stresses inability to fix the mind on present concerns due more to mental wandering than to concentration on other matters.
// an absent stare absentminded implies that the mind is fixed elsewhere and often refers to a habit of abstractedness.
// so absentminded, he's been known to wear mismatched shoes distracted may suggest an inability to concentrate caused by worry, sorrow, or anxiety.
// was too distracted by grief to continue working