|Noah Webster's Dictionary|
1. (v. t.) To accuse falsely and maliciously of a crime or offense, or of something disreputable; to slander; to libel.
2. (v. i.) To propagate evil reports with a design to injure the reputation of another; to make purposely false charges of some offense or crime.
Calumniate (1 Occurrence)
1 Peter 3:16 having a good conscience, that as to that in which they speak against you as evildoers, they may be ashamed who calumniate your good conversation in Christ. (DBY)