Definition of: unwritten law

1. A rule or custom established by general usage: an unwritten law of gentlemanly decorum.
2. Law which rests on custom and judicial decision, and not on a written command, decree, or statute. See COMMON LAW under LAW.
3. A custom in some communities granting a measure of immunity to those who commit criminal acts of revenge in support of personal or family honor, especially in cases of seduction, adultery, etc.