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.(noun)
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Use "backbiter" in a sentence
"Accordingly a backbiter is a murderer _occasionally, _ since by his words he gives another man an occasion for hating or despising his neighbor."
"Reply Obj. 1: A tale-bearer is called a backbiter in so far as he speaks ill of another; yet he differs from a backbiter since he intends not to speak ill as such, but to say anything that may stir one man against another, though it be good simply, and yet has a semblance of evil through being unpleasant to the hearer."
"'And many other are there, good and great; and one, Loki, fair of face, ill in temper and fickle of mood, is called the backbiter of the Asa, and speaker of evil redes and shame of all gods and men; he has above all that craft called sleight, and cheats all in all things."