A Plea

1. An appeal, petition, urgent prayer or entreaty.
2. An excuse; an apology.
3. That which is alleged or pleaded, in defense or in justification.
4. (law) That which is alleged by a party in support of his cause.
5. (law) An allegation of fact in a cause, as distinguished from a demurrer.
6. (law) The defendant’s answer to the plaintiff’s declaration and demand.
7. (law) A cause in court; a lawsuit; as, the Court of Common Pleas.

In 19th century U.K. law, that which the plaintiff alleges in his declaration is answered and repelled or justified by the defendant’s plea. In chancery practice, a plea is a special answer showing or relying upon one or more things as a cause why the suit should be either dismissed, delayed, or barred. In criminal practice, the plea is the defendant’s formal answer to the indictment or information presented against him/her.