1. To pay attention to or to think about something constantly and obsessively: James was a journalist who was fixating on scandals much more than normal events.
2. To bond oneself to an individual in an emotionally disturbed way: Ever since Larry was a little boy, he has not gone anywhere without his mother being fixated on him.
3. To be totally obsessed or preoccupied with somebody or something: Frank wants to be the best pianist ever, so he is fixating on practicing about five to six hours every day.