The person defending or denying; the party against whom relief or recovery is sought in an action or suit, or the accused in a criminal case.
In every legal action, whether civil or criminal, there are two sides. The person suing is the plaintiff and the person against whom the suit is brought is the defendant. In some instances, there may be more than one plaintiff or defendant.
If an individual is being sued by his or her neighbor for TRESPASS, then he or she is the defendant in a civil suit. The person being accused of murder by the state in a HOMICIDE case is the defendant in a criminal action.