1) In criminal law, a declaration that a law is invalid because it is not sufficiently clear. Laws are usually found void for vagueness if, after setting some requirement or punishment, the law does not specify what is required or what conduct is punishable. For more information, see vagueness doctrine.
2) Under vagueness doctrine, a statute is also void for vagueness if a legislature's delegation of authority to judges and/or administrators is so extensive that it would lead to arbitrary prosecutions.
3) In property law, a declaration that a deed or other instrument purporting to affect property rights is invalid because it lacks a sufficiently clear description of the property.