Available Definitions:
1) a. - Appertaining to a decree; containing a decree; as, a decretal epistle.
2) a. - An authoritative order or decree; especially, a letter of the pope, determining some point or question in ecclesiastical law. The decretals form the second part of the canon law.
3) a. - The collection of ecclesiastical decrees and decisions made, by order of Gregory IX., in 1234, by St. Raymond of Pennafort.