Definition of Feriae
In Roman law, holidays; generally speaking, days or seasons during which free-born Romans suspended their political transactions and their lawsuits, and during which slaves enjoyed a cessation from labor.
All feriae were thus dies nefasti. All feria: were divided into two classes,—"feria: publicae” and "feriae privates.” The latter were only observed by single families or individuals, in commemoration of some particular event which had been of importance to them or their ancestors.
Numerous festivals were called by this name in the early Roman empire. In the later Roman empire the single days occurring at intervals of a week apart, commencing with the seventh day of the ecclesiastical year, were so called.
That's the definition of Feriae in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.