Law . failure of a professional person, as a physician or lawyer, to render proper services through reprehensible ignorance or negligence or through criminal intent, esp. when injury or loss follows.

any improper, negligent practice; misconduct or misuse.

noun

carelessness , dereliction , malefaction , misbehavior , misdeed , mismanagement , negligence , offense , transgression , violation , evil practice , misconduct , misdoing