Synonyms:
defamer, maligner, slanderer, vilifier, libeler, backbiter, traducer
Meaning: one who attacks the reputation of another by slander or libel
Usage examples
"Ignorant and stupid as Deerbrook is about many things, Priscilla, it is not so wicked as to thank any one for waging a cowardly war against the good, for disparaging the able and accomplished, and fabricating and circulating injurious stories against people too magnanimous for the slanderer to understand."