Constitution

In public law. The organic and fundamental law of a nation or state, which may be written or unwritten, establishing the character and conception of its government, laying the basic principles to which its internal life is to be conformed, organizing the government, and regulating, distributing, and limiting the functions of its different departments, and prescribing the extent and manner of the exercise of sovereign powers. In a more general sense, any fundamental or important law or edict; as the Novel Constitutions of Justinian; the Constitutions of Clarendon.

In American law

The written instrument agreed upon by the people of the Union or of a particular state, as the absolute rule of action and decision for all departments and officers of the government in respect to all the points covered by it, which must control until it Bhall be changed by the authority which established it, and in opposition to which any act or ordinance of any such department or officer is null and void.

Cooley, Const. Lim. 8.