Wiktionary
n. A policy or set of rules from which a constitution can be developed.
Wikipedia
A metaconstitution is a set of pre-constitutional rules. It is in lieu of a formalized constitution and consists of accepted axiomatic policy. The constitution is similar to or developed from this. A metaconstitution is also less binding, and can be used to a less rigid form of government. To many nations, the metaconstitution provides an "exit-option", where they may variate from the written document. A metaconstitution, unlike formal constitutions, never needs to be written. Its creation results from the morality and judgment of the people. To be formulated, the people must be generally opposed to anarchy and must desire some form of governing force.
Although vague in concept, the metaconstitution almost always creates the basic roles of leader v. follower. The purpose of the document, however, prevents the placement of total power on the leader. The populace is trusted to self-govern except in severe cases. Such theory does not differ much from salutary neglect or laissez faire.