the GNU version of the Collaborative International Dictionary of English
n. One who calumniates.
The Century Dictionary and Cyclopedia
n. One who calumniates or slanders; one who falsely and knowingly accuses another of anything of a disgraceful character, or maliciously propagates false accusations or reports.
""'There is another deity,' continued Har, 'reckoned in the number of the Æsir, whom some call the calumniator of the gods, the contriver of all fraud and mischief, and the disgrace of gods and men."