In the manner of a falsification intended to discredit another.(adverb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "calumniously" in a sentence
"But bring any of these trespasses up as some of the threads running through the tapestry of our history and he who so utters them will be assailed as unpatriotic, un-American, traitorous, treasonous, and anything else that might paint that truth-teller calumniously."
"The persons who were most bitter against him even declared calumniously that he had made over a large amount of property to Dumay to save it from the just demands of his associates in China."
"Will not all who have sided against him in this most singular adventure, charge him with calumniously accusing his adversaries of a crime of which he is himself guilty?"