Dictionary.net

Performing a legal action in an improper way. This term is frequently used when a professional or public official does his job in a way that is not technically illegal, but is nevertheless mistaken or wrong. Here are some examples of misfeasance in a professional context: a lawyer who is mistaken about a deadline and files an important legal document too late, an accountant who makes unintentional errors on a client's tax return or a doctor who writes a prescription and accidentally includes the wrong dosage. Compare malfeasance.

n. [Normandic, French, Latin] A trespass; a wrong done.