(Functioning) automatically, without thinking about one's actions, generally because one has done something many times in the past. By the second week of data entry, I could fill in the spreadsheets on automatic. Making bottles, changing diapers, and putting the baby to sleep were all challenging at first, but now I feel like I'm doing it all on automatic. Sometimes I arrive at work without remembering how I got there, like I was on automatic the whole time.