What is Adnotatio?

Legal Definition
In the Civil law. The subscription of a name or signature to an instrument. Co.d. 4, 19, 5, 7. A rescript of the prince or emperor, signed with his own hand, or sign-manual. Coke 1, 19, 1. "In the imperial law, casual homicide was excused by the indulgence of the emperor, signed with hla own sign-manual, annotatione principis." 4 Bl. Comm. 187.
-- Black's Law Dictionary