1. inaccuracy, erratum, fault, oversight. Mistake, blunder, error, slip refer to deviations from right, accuracy, correctness, or truth. A mistake, grave or trivial, is caused by bad judgment or a disregard of rule or principle: It was a mistake to argue. A blunder is a careless, stupid, or gross mistake in action or speech, suggesting awkwardness, heedlessness, or ignorance: Through his blunder the message was lost. An error (often interchanged with mistake ) is an unintentional wandering or deviation from accuracy, or right conduct: an error in addition. A slip is usually a minor mistake made through haste or carelessness: a slip of the tongue. 4. misconceive, misjudge, err.