A person who is being sued, the party against whom a lawsuit is filed. In some instances, the plaintiff may be called the petitioner and the defendant the respondent. The person defending or denying; the party against whom relief or recovery is sought in an action or suit. In common usage, this term is applied to the party put upon his defense, or summoned to answer a charge or complaint, in any species of action, civil or criminal, at law or in equity. Strictly, however, it does not apply to the person against whom a real action is brought, for in that proceeding the technical usage is to call the parties respectively the “demandant” and the “tenant.”. Defendant in error. The distinctive term appropriate to the party against whom a writ of error is sued out.