For the purpose of this subchapter—

(1) the term “missing child” means any individual less than 18 years of age whose whereabouts are unknown to such individual’s parent;

(2) the term “Administrator” means the Administrator of the Office of Juvenile Justice and Delinquency Prevention;

(3) the term “Center” means the National Center for Missing and Exploited Children; and

(4) the term “parent” includes a legal guardian or other individual who may lawfully exercise parental rights with respect to the child.