Calumniate -

: Unlike simple "lying," calumniating specifically targets a person's character or reputation with the intent to harm.

To means to spread malicious, false statements about someone to damage their reputation. It is essentially a formal way to say you are lying about someone to make them look bad. Essential Guide to "Calumniate" calumniate

: To make false and defamatory statements maliciously. : Unlike simple "lying," calumniating specifically targets a