What is Calumniator?

Legal Definition
Civil law. Persons who accuse others, whom they know to be innocent, of having committed crimes. Code 9, 46, 9.
-- Bouviers Law Dictionary
Legal Definition
In the civil law. One who accused another of a crime without cause; one who brought a false accusation. Cod. 9, 46.
-- Black's Law Dictionary
Legal Definition
Those who make false accusations maliciously.
-- Ballentine's Law Dictionary