Which term is defined as an affirmative act that is illegal or wrongful?

The term defined as an affirmative act that is illegal or wrongful is considered malfeasance. This concept refers to a specific type of wrongdoing where an individual performs a lawful act in an illegal or harmful manner, or engages in actions that directly contravene legal statutes or duties. In the context of medical law, malfeasance can occur when a healthcare professional takes an action that is clearly harmful, such as performing a procedure improperly, which can lead to patient harm and legal liability.

Malpractice and negligence, although related to wrongful acts in the medical profession, refer more to breaches of duty rather than an affirmative illegal act. Malpractice involves failure to meet standard care, while negligence generally pertains to unintentional harm due to carelessness. Defamation, on the other hand, involves damaging someone's reputation through false statements and does not fit the definition of an affirmative illegal or wrongful act in the same way that malfeasance does. Therefore, malfeasance best fits the description given in the question.