calumniate

Etymology

From Latin calumniātus, perfect active participle of calumnior (“I accuse falsely”).

verb

1. (transitive) To make hurtful untrue comments about.
   Hatred unto the truth did always falsely report and calumniate all godly men's doings. a. 1555, John Hooper, A Brief Treatise respecting Judge Hales
   There are adherents of each of the four French parties—Legitimists, Orleanists, Imperialists, and Republicans—in this little mountain-town; and they all hate, loathe, decry, and calumniate each other. 1905, Robert Louis Stevenson, “chapter 1”, in Travels with a Donkey in the Cevennes
2. (transitive) To levy a false charge against, especially of a vague offense, with the intent to damage someone's reputation or standing.