Ghība (backbiting) is to mention your brother with something that he would dislike if he heard it. This fault may pertain to his body, lineage, character, actions, speech, religion, or even his clothing, house, animal—wherever it may be, it makes no difference. (Iḥyāʾ, III, 177)
Ghība is to mention someone who is absent with something he would dislike to hear. This is forbidden (ḥarām) for the believers (muʾmin). Allah is not absent, for in the first instance and according to the scholars, He is the All-Hearing, the All-Seeing. He has made manifest those things which His servants would dislike and those for which He has praised Himself. Among His servants are those who have iman (faith) and those who are kuffār (disbelievers). Likewise, the names of agent (fāʿil) and object (mafʿūl) are also not absent.
Ghība is also forbidden (ḥarām) for those who are legally responsible (mukallaf) due to things that cause enmity between them. Outside of the believers, people of virtue (ahl al-murūʾa) also avoid it out of refinement and the nobility of the nafs (the lower self). Their avoidance of it, especially in private settings, indicates the nobility of their method. Surely, this is necessary and is a means of drawing near to Allah. Among the believers, those who are people of waraʿ (scrupulousness) indicate this by allusion and do not state it openly. The reason why the hadith scholars (muḥaddithūn) criticize narrators who transmit the legal rulings of the sharia (the sacred law) is because of this.
It has been narrated to us from some of the scholars who possess maʿrifa (gnosis, experiential knowledge of God): one of them would say to his companion, "Come, let us speak about Allah," or, "Let us discuss the matter of marriage consultation." Surely, this is a trustworthy ḥāl (spiritual state). Sincerity (ikhlas) is also necessary. There is also the matter of ghībat al-ghumma (veiled backbiting)...