To plead. 1. To argue in support of a claim, or in defense against the claim of another; to urge reasons for or against a thing; to attempt to persuade one by argument or supplication; to speak by way of persuasion; as, to plead for the life of a criminal; to plead with a judge or with a father. 2. To discuss, defend, and attempt to maintain by arguments or reasons presented to a tribunal or person having uthority to determine; to argue at the bar; as, to plead a cause before a court or jury.