b: an act involving an unintentional deviation from truth or accuracy 〈made an error in adding up the bill〉 c: an act that through ignorance, deficiency, or accident departs from or fails to achieve what should be done 〈an error in judgment〉: as (1): a defensive misplay other than a wild pitch or passed ball made by a baseball player when normal play would have resulted in an out or prevented an advance by a base runner (2): the failure of a player (as in tennis) to make a successful return of a