What is Brevia Formata?

Legal Definition
Eng law. The collection of writs found in the Registrum Brevium was so called. The author of Fleta says, these writs were formed upon their cases. They were different from the writs de cursu, which were approved by the council of the whole realm, and could not be changed without the will of the same. Fleta, lib. 2, c. 13, ยง2. See 17 S. & R. 194-5, and authorities there cited.
-- Bouviers Law Dictionary
Legal Definition
Certain write of approved and established form which were granted of course in actions to which they were applicable, and which could not be changed but by consent of the great council of the realm. Bract, fol. 4136.
-- Black's Law Dictionary