Backbiting

The Prophet (pbuh) defined backbiting when he said: "Do you know what is meant by backbiting ?" They said, "Allah and His Messenger know best." He said, "To say something about your brother which he dislikes." One asked, "Even if what I say is true about my brother?" He replied, "If such defects you say are true about him, then you have backbitten him, and if he doesn't have what you say, then you have committed slander against him." (Related by Muslim, Abu Dawood, and Tirmidhi)