adjective

(of remarks, writing, etc.) damaging the good reputation of someone; slanderous or libellous.

a defamatory allegation

libellous,slanderous,defaming,calumnious,calumniatory,vilifying,traducing,scandalous,scandalmongering,malicious,vicious,backbiting,muckraking,abusive,maledictory,maledictive,disparaging,denigratory,detracting,derogatory,censorious,critical,insulting,slurring,injurious,mud-slinging,bitchy,catty,contumelious