Meaning of unwritten law

unwrit'ten law'

Pronunciation: [key]
  1. a law that rests for its authority on custom, judicial decision, etc., as distinguished from law originating in written command, statute, or decree.
  2. the supposed principle of the right of the individual to avenge wrongs against personal or family honor, esp. in cases involving relations between the sexes: sometimes urged in justification of persons guilty of criminal acts of vengeance.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.