1) Backbiter 2) Defamer 3) Depreciator 4) Detractor 5) Disparager 6) Knocker 7) Libeler 8) Maligner 9) Traducer 10) Vilifier 1) Backbiter 2) Defamer 3) Libeler 4) Maligner 5) Traducer 6) Vilifier 
• (n.) One who slanders; a defamer; a calumniator.
Slan'der·er noun One who slanders; a defamer; a calumniator. Jer. Taylor. 
A calumniator, who maliciously and without reason imputes a crime or fault to another, of which he is innocent. For this offence, when the slander is merely verbal, the remedy is an action on the case for damages; when it is reduced to writing or printing, it is a libel.