What is "extravagantes"

The term Extravagantes (from the Latin extra, outside; vagari, to wander) is applied to the canon law of the Roman Catholic Church, to designate some papal decretals not contained in certain canonical collections which possess a special authority. More precisely, they are not found in Gratian's ' Decretum or the three official collections of the Corpus Juris Canonici (the Decretals of Gregory IX, the Sixth Book of the Decretals, and the Clementines).