Definitions for backbiter
Random House Webster's College Dictionary
back•biteˈbækˌbaɪt(v.)-bit, -bit•ten; -bit; -bit•ing.
(v.t.)to attack the character or reputation of (a person not present).
(v.i.)to slander an absent person.
Origin of backbite:
defamer, maligner, slanderer, vilifier, libeler, backbiter, traducer(noun)
one who attacks the reputation of another by slander or libel
person who says nasty things about another person behind the second person's back: that is, out of sight and hearing of the second person.
one who backbites; a secret calumniator or detractor
The Foolish Dictionary, by Gideon Wurdz