Synonyms for Calumnious (same or very similar meaning)
WordNet sense 1 ((used of statements) harmful and often untrue; tending to discredit or malign):
defamatory, libellous, libelous, slanderous, calumniatory, denigrating, denigrative, denigratory
WordNet sense 2 (causing or capable of causing harm):
harmful
From the ODE community, based on WordNet
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