Noah Webster's Dictionary (n.) Secret slander; detraction.

Multi-Version Concordance Backbiting (2 Occurrences) Psalms 35:16 Like the profane mockers in feasts, They gnashed upon me with their teeth. (See JPS) Proverbs 25:23 The north wind brings forth rain: so a backbiting tongue brings an angry face. (WEB KJV JPS ASV DBY WBS NAS RSV)