Misfeasance is best described as:

Misfeasance refers specifically to the improper performance of a lawful act. In legal terms, it means that an individual had a duty to act and did act, but did so in a way that was inappropriate or inefficient, thereby resulting in harm or damage. This contrasts with nonfeasance, where there is a failure to act at all, and malfeasance, which involves intentional wrongdoing.

By defining misfeasance as performing a task improperly, it captures the essence of the term: there is an expectation of the action being executed correctly due to a pre-existing duty, yet the actor deviates from that expectation, leading to adverse consequences. This concept is particularly relevant in contexts where professionals are expected to meet certain standards of care or conduct, as any failure to adhere to these standards can result in liability for damages.

The other definitions do not align with the specific parameters of misfeasance. Neglecting to act refers to nonfeasance, intentionally causing harm relates to malfeasance, and unintentionally making a mistake does not capture the essence of the improper execution of a duty. Thus, defining misfeasance as performing a task improperly accurately reflects its legal understanding and implications.