From Middle English, from Old French plait, plaid, from Medieval Latin placitum (“a decree, sentece, suit, plea, etc., Latin an opinion, determination, prescription, order; literally, that which is pleasing, pleasure”), neuter of placitus, past participle of placere (“to please”).
plea (plural pleas)
- An appeal, petition, urgent prayer or entreaty.
- a plea for mercy
- An excuse; an apology.
- That which is alleged or pleaded, in defense or in justification.
- (law) That which is alleged by a party in support of his cause.
- (law) An allegation of fact in a cause, as distinguished from a demurrer.
- (law) The defendant’s answer to the plaintiff’s declaration and demand.
- (law) A cause in court; a lawsuit; as, the Court of Common Pleas. See under Common.
- (Can we date this quote?) The Supreme Judicial Court shall have cognizance of pleas real, personal, and mixed. --Laws of Massachusetts.
Usage notes 
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.
Related terms 
- The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.
- plea in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
- plea in The Century Dictionary, The Century Co., New York, 1911
- plea at OneLook Dictionary Search