What is A defense that must be specifically pled classified as?

A defense that must be specifically pled is classified as an "affirmative defense." This type of defense requires the defendant to not only deny the allegations but also to present additional facts or legal arguments that, if proven, would negate liability or reduce culpability. Examples include self-defense in criminal cases or statute of limitations in civil cases. Failing to adequately plead an affirmative defense may result in it being waived in court.